Injection device

Abstract

This injection device is characterized by being provided with an engagement releasing mechanism that moves a plunger from a start point to an end point by the biasing force of a plunger biasing unit and relatively rotates the plunger and an engagement member about a central axis to release engagement between the plunger and the engagement member and locate the plunger at the end point.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority based on Japanese Patent Application No. 2020-023484, the entire disclosure of which is incorporated herein by reference. [Technical field]

[0002] The present invention relates to an injection device in which the needle can be withdrawn from the housing during use and returned into the housing after use. [Background technology]

[0003] A syringe capable of retracting a needle that has come out of the barrel is described in Patent Document 1. This syringe has a front end and a middle part that accommodate a capsule having a needle, slidably between a state in which the needle protrudes to the outside and a state in which the needle is accommodated inside. This syringe also has a rear part that is continuous with the middle part and can accommodate a plunger extending rearward from the capsule. In addition, the syringe has a barrel with an annular rib that separates the middle part from the rear part, one coil spring that is accommodated in the middle part and urges the capsule toward the annular rib, a driving member that is accommodated in the rear part and engages with the rear end of the rod of the plunger, the other coil spring that is accommodated in the rear part and engages with the driving member to urge the rod to move toward the needle, and a cap that is provided in the rear part and engages with the driving member so as not to release the urging of the other coil spring in a maximum compression state, and is configured to release the engagement by a predetermined operation. The rear end of the rod is bifurcated to form a bifurcated end having a protrusion at the base and a balanced portion at the tip. The protrusion is configured to abut against an inner surface of the capsule when the rod reaches the forward end of its travel. The drive member has an annular bottom that engages with the mating portion.

[0004] According to this syringe, when the cap is operated, the cap and the driving member are disengaged, and the driving member moves toward the front end side due to the bias of the other coil spring, which was in a maximum compression state. When the driving member moves toward the front end side, the capsule housing the tip side of the rod that engages with the driving member moves toward the front end side due to the balanced portion, and one of the coil springs housed in the middle part is compressed toward the front end side. When the capsule moves toward the front end side, the injection needle at the tip of the capsule protrudes out of the barrel, and then the rod is pushed by the driving member, and the plunger advances inside the capsule. When the plunger reaches the moving end on the front side, the protrusion hits the inner surface of the capsule, the forked end narrows, and the engagement between the annular bottom of the driving member and the balanced portion is released. Then, one of the coil springs compressed toward the front end side is released, and the capsule moves backward due to the bias of the one of the coil springs, and the injection needle protruding from the tip of the barrel is retracted. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent No. 3292747

[0006] However, in the above conventional syringe, the mechanism for releasing the engagement between the joint of the rod and the annular bottom of the drive member is a mechanism in which a protrusion provided at the base of the forked part abuts against the inner surface of the capsule to narrow the forked end. Therefore, due to an error in the length or size of the forked end, or an error in the position or size of the protrusion, the forked end may not be narrowed enough to release the engagement even when the protrusion abuts against the inner surface of the capsule. In this case, even if the injection needle protrudes and the rod reaches the forward moving end, the other compressed spring is not released, and the capsule does not return, which is dangerous. Summary of the Invention [Problem to be solved by the invention]

[0007] Therefore, an object of the present invention is to provide an injection device that can reliably return the injection needle. [Means for solving the problem]

[0008] The present invention relates to a syringe having a barrel with an injection needle at its tip, and a plunger inserted into the barrel so as to be reciprocally movable between the base end side of the barrel and the injection needle side; and a cylindrical housing for accommodating the syringe, the housing having a barrel accommodating section formed on one side in the central axial direction for accommodating the barrel so as to be movable 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 at a predetermined distance to one side from the accommodated state, and a plunger accommodating section formed on the other side of the barrel accommodating section for accommodating the plunger protruding from the base end side of the barrel. The housing further comprises a barrel biasing section provided in the barrel accommodating section for biasing the barrel from one side of the housing to the other side, and a plunger accommodating section for biasing the plunger from the one side of the housing to the other side. and a trigger portion configured to hold the force of the plunger biasing portion from being released when the barrel is placed in a state in which the injection needle is housed in the barrel by the barrel biasing portion and the tip of the plunger is located at the start point position against the biasing force of the plunger biasing portion, and to release the hold when a predetermined operation is performed. The injection device is characterized in that it comprises an engagement member that engages with the barrel, a plunger biasing portion that engages with the engagement member and biases the plunger from the start point to the end point, and a trigger portion configured to hold the plunger from being released when the plunger biasing portion moves from the start point to the end point by the biasing force of the plunger biasing portion, and to relatively rotate the plunger and the engagement member about a central axis, thereby releasing the engagement between the plunger and the engagement member and positioning the plunger at the end point.

[0009] In addition, in the injection device, the disengagement mechanism may include a rotational engagement portion provided on the plunger and a rotational engaged portion provided on the barrel, and is configured such that when the plunger moves from the starting point to the end point and the rotational engagement portion engages with the rotational engaged portion, the plunger rotates about the central axis and disengages the plunger from the engaging member.

[0010] In addition, the injection device may be configured such that when the plunger moves from the starting point to just before reaching the end point, the rotational engagement portion engages with the rotational engaged portion, causing the plunger to rotate about the central axis and releasing the engagement between the plunger and the engagement member.

[0011] In addition, the plunger biasing portion may be configured to bias the engaging member in a direction in which the engaging member rotates around a central axis, and the disengagement mechanism may be configured to disengage the plunger from the engaging member by rotating the engaging member around the central axis relative to the plunger using the biasing force of the plunger biasing portion.

[0012] The plunger biasing portion may be a torsion spring, and the engaging member may be rotated by the biasing force of the torsion spring. [Brief description of the drawings]

[0013] [Figure 1] FIG. 1 is a front view of an injection device according to an embodiment of the present invention, with the housing shown in cross-section. [Diagram 2] FIG. 2 is a cross-sectional view of the housing according to the embodiment. [Diagram 3] FIG. 3 is an exploded perspective view of the syringe of the embodiment. [Figure 4] FIG. 4 is a plan view of the syringe of the same embodiment. [Diagram 5] FIG. 5 is a right side view of the syringe of the injection device of the embodiment, showing a cross section of the barrel and the piston. [Figure 6] FIG. 6 is a front view of the engaging member of the embodiment. [Figure 7] FIG. 7 is a bottom view of the engagement member. [Figure 8] FIG. 8 is a cross-sectional view of the engaging member taken along the line VIII-VIII. [Figure 9]FIG. 9 is a front view showing the injection device of the same embodiment in an exploded state, with the housing and the cap shown in cross section. [Figure 10] FIG. 10 is a front view of the injection device according to the embodiment in an initial state, showing the housing and the cap in cross section. [Figure 11] FIG. 11 is a diagram showing the disengagement mechanism in the injection device in the initial state. [Figure 12] FIG. 12 is a diagram showing the injection device of the same embodiment, in which the housing is in cross section and the injection needle is pulled out of the housing. [Figure 13] FIG. 13 is a diagram showing the injection device of this embodiment, illustrating a cross section of the housing and a state in which the rotation engaging portion and the rotation engaged portion are engaged with each other. [Figure 14] FIG. 14 is a diagram showing the injection device of the same embodiment, in which the housing is in cross section and the plunger is rotated about the central axis. [Figure 15] FIG. 15 is a diagram showing the disengagement mechanism in a state where the plunger has rotated about the central axis. [Figure 16] FIG. 16 shows the injection device of the same embodiment with the housing in cross section and the injection needle inserted back into the housing. [Figure 17] FIG. 17 is a diagram showing a state in which the anti-rotation fitting portion and the anti-rotation fitted portion are fitted together when the injection needle is returned into the housing. [Figure 18] FIG. 18 is a perspective view of an engagement member, a rod, and a cover portion according to a modified example of the injection device. [Figure 19] FIG. 19 is a cross-sectional view of a plunger housing portion according to a modified example of the injection device. [Figure 20] FIG. 20 is a cross-sectional view of a plunger housing according to a second embodiment of the injection device. [Figure 21] FIG. 21 is a side view of the syringe according to the same embodiment. [Figure 22] FIG. 22 is a perspective view of the engaging member according to the same embodiment. [Diagram 23]FIG. 23 is a front view of the injection device according to the embodiment, showing a cross section of the housing, illustrating a state immediately before the engagement between the rotation engaging portion and the rotation engaged portion is released. [Figure 24] FIG. 24 is a detailed view showing a state immediately before the engagement between the rotation engaging portion and the rotation engaged portion is released. [Diagram 25] FIG. 25 is a front view of the injection device according to the embodiment, showing a cross-section of the housing and a state in which the rotational engagement portion and the rotationally engaged portion are disengaged from each other. [Figure 26] FIG. 26 is a detailed view showing a state in which the rotational engaging portion and the rotationally engaged portion are disengaged from each other. [Figure 27] FIG. 27 is a front view of the injection device according to the embodiment, showing the housing in cross section and the engagement member rotated about the central axis. [Figure 28] FIG. 28 is a detailed view showing a state in which the engaging member is rotated around the central axis. [Figure 29] FIG. 29 is a partially enlarged cross-sectional view of a syringe according to a modified example of the injection device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Hereinafter, embodiments of the injection device of the present invention will be described. First, the structure of an injection device 1 of a first embodiment will be described.

[0015] The injection device of this embodiment is used, for example, when a patient administers a liquid medicine such as insulin or a rheumatoid drug to his or her own body, and the injection needle protrudes from the device during injection and returns to the device after injection. As shown in FIG. 1, the injection device 1 of this embodiment accommodates a syringe 10 filled with a liquid medicine, an engagement member C engaged with a plunger 12 of the syringe 10, a plunger biasing part A engaged with the engagement member C, and a barrel biasing part B engaged with a barrel 11 of the syringe 10 in a housing 2 extending along a central axis O. In the following figures, O is the central axis, and the upper side in FIG. 1 is referred to as the "base end side" and the lower side is referred to as the "tip side".

[0016] FIG. 1 is a front view of the injection device 1 of the present embodiment, in which the housing 2 is cut along the central axis O. The housing 2 is formed to accommodate the syringe 10. Specifically, the housing 2 is formed in a cylindrical shape to cover the syringe 10. In this embodiment, the housing 2 is formed in a cylindrical shape. In addition, in this embodiment, in the direction of the central axis O, the base end side is closed by a trigger portion 23, and the tip end side is formed in a cylindrical shape that is open to allow the injection needle 13 to protrude outside the device.

[0017] The housing 2 has a partition 22 that partitions the inside of the cylinder at a midpoint in the direction of the central axis O. A barrel accommodating section 21 that accommodates the barrel 11 is formed on one side of the partition 22 in the housing 2. In the barrel accommodating section 21, the barrel 11 is configured to be movable between a first position where the barrel 11 abuts against the partition 22 and accommodates the injection needle 13 in the housing 2 (see Figs. 1 and 10) and a second position where the barrel 11 moves a predetermined distance away from the partition 22 to one side and thereby the injection needle 13 protrudes from one side of the housing 2 (see Fig. 12). In addition, a plunger accommodating section 20 that accommodates the plunger 12 protruding from the base end side of the barrel 11 is formed on the other side of the partition 22 in the housing 2.

[0018] The plunger accommodating portion 20 extends from the partition portion 22 toward the base end side of the central axis O. As shown in Fig. 1, the plunger accommodating portion 20 accommodates a plunger biasing portion A, an engaging member C, and a plunger 12 in this order from the base end side to the tip end side.

[0019] As shown in FIG. 2, the plunger accommodating portion 20 includes a biasing base portion 200 that abuts against the plunger biasing portion A described later. The biasing base portion 200 protrudes radially inward from the inner peripheral surface of the cylindrical plunger accommodating portion 20. The biasing base portion 200 includes an insertion hole 200b that is centered on the central axis O and communicates the inside and outside of the plunger accommodating portion 20 along the central axis O. Therefore, the biasing base portion 200 is formed in an inner flange shape within the plunger accommodating portion 20. The biasing base portion 200 includes a tip-side protrusion 200a that protrudes toward the tip side in the direction of the central axis O and prevents the plunger biasing portion A from moving in the radial direction. The tip-side protrusion 200a is inserted into the plunger biasing portion A described later.

[0020] The plunger accommodating portion 20 includes an engagement and holding mechanism Y1 that holds the engaging member C so as not to rotate relative to the plunger accommodating portion 20. In this embodiment, as shown in FIG. 2, the plunger accommodating portion 20 includes a holding protrusion 201 as the engagement and holding mechanism Y1 on its inner circumferential surface. The holding protrusion 201 protrudes radially inward from the inner circumferential surface of the plunger accommodating portion 20. The holding protrusion 201 is continuously formed in the direction of the central axis O from the base end side to the tip end side of the plunger accommodating portion 20. In addition, the holding protrusion 201 is provided in a plurality of positions spaced apart from each other in the circumferential direction. In this embodiment, four holding protrusions 201 are provided at intervals in the approximately cylindrical plunger accommodating portion. Specifically, the holding protrusion 201 includes a pair of first holding protrusions 201a that are fitted in a first holding recess C40 (described later) and a pair of second holding protrusions that are fitted in a second holding recess C41. The pair of first retaining protrusions 201a and the pair of second retaining protrusions are arranged to face each other in the radial direction on the inner circumferential surface of the substantially cylindrical plunger accommodating portion 20. The first retaining protrusions 201a have a smaller circumferential width than the second retaining protrusions. An engaging member C, which will be described later, moves in the direction of the central axis O while being restricted from rotating around the central axis O via the retaining protrusions 201. As shown in FIG. 2, the plunger accommodating portion 20 has a larger diameter both inside and outside the cylinder at its tip side. The partition portion 22 and the base end portion of the barrel accommodating portion 21 are accommodated in the tip side of the plunger accommodating portion 20.

[0021] The plunger accommodating portion 20 is provided with a through hole 202 penetrating in the radial direction. The through hole 202 is provided along the circumferential surface of the cylindrical plunger accommodating portion 20 and at a position adjacent to the first holding protrusion 201a as shown in Fig. 2. In this embodiment, a pair of the through holes 202 are provided so as to face each other in the radial direction.

[0022] As shown in FIG. 1, the plunger accommodating portion 20 is engaged with the engaging member C. The plunger urging portion 20 accommodates a plunger urging portion A that urges the plunger 12 from the starting point toward the end point. In this embodiment, the starting point is a position on the tip side of the base end of the barrel 11 shown in FIG. 5. In this embodiment, the end point is the tip of the barrel 11. Specifically, the plunger urging portion A in this embodiment is configured by a compression coil spring wound around the central axis O. In addition, an engaging member C, which will be described later, is inserted into the plunger urging portion A accommodated in the plunger accommodating portion 20. Then, one end of the plunger urging portion A in the direction of the central axis O abuts against the urging base portion 200, and the other end abuts against the urging receiving portion C2 of the engaging member C. Therefore, in this embodiment, in the state shown in FIG. 1, the plunger urging portion A is compressed by the engagement member C approaching the urging base portion 200.

[0023] The housing 2 includes a barrel accommodating portion 21 on the tip side of the central axis O, sandwiching the partition portion 22. The barrel accommodating portion 21 is formed so as to be continuous with the plunger accommodating portion 20 via the partition portion 22. The barrel accommodating portion 21 is formed in a cylindrical shape penetrating in the direction of the central axis O. Therefore, the plunger 12 inserted into the barrel 11 from the base end of the barrel accommodating portion 21 can extend into the plunger accommodating portion 20, and the injection needle 13 can protrude from the tip of the barrel accommodating portion 21.

[0024] As shown in FIG. 2, the barrel housing 21 is formed in a stepped cylinder shape in which the inner diameter and the outer diameter on the base end side are larger than the inner diameter and the outer diameter on the tip end side. Therefore, the barrel housing 21 includes a large barrel side barrel housing 210 having a larger inner diameter and an outer diameter on the base end side, and a small barrel side barrel housing 211 formed on the tip side of the large barrel side barrel housing 210 and having a smaller outer diameter and inner diameter than the large barrel side barrel housing 210. The large barrel side barrel housing 210 includes a barrel receiving part 210a that receives the barrel 11 that has moved to the tip side by the biasing force of the plunger biasing part A, and a rotation holding mechanism X that holds the cover part 111 of the barrel 11, which will be described later, so that it does not rotate with respect to the barrel housing 21. The barrel receiving part 210a is located at a step where the base end of the small barrel side barrel housing 211 and the tip of the large barrel side barrel housing 210 are continuous. The barrel receiving part 210a is formed over the entire circumference inside the barrel housing 21. The rotational holding mechanism X is formed in the large barrel housing 210. Specifically, the rotational holding mechanism X in this embodiment is formed continuously along the central axis O so as to extend from the partition 22 to the barrel receiving part 210a in the large barrel housing 210. The rotational holding mechanism X in this embodiment is formed as a holding protrusion 210b that engages with a holding recess 111b formed in the cover part 111 of the barrel 11 described later. This holding protrusion 210b protrudes toward the inside of the barrel housing 21. In this embodiment, the holding protrusions 210b are provided in a plurality of positions spaced apart from each other in the circumferential direction. Specifically, a pair of the holding protrusions 210b is provided in a direction perpendicular to the central axis O.

[0025] The barrel accommodating portion 21 includes a biasing base portion 211a against which the barrel biasing portion B comes into contact. As shown in Fig. 1, the biasing base portion 211a is provided protruding into the small cylinder side barrel accommodating portion 211 on the tip side of the cover portion 111 (barrel receiving portion 210a). This biasing base portion 211a protrudes along the inner circumferential surface of the barrel accommodating portion 21. The biasing base portion 211a is formed in an inner flange shape that fits along the inner surface of the small cylinder side barrel accommodating portion 211 so that the barrel 11 can be inserted.

[0026] The partition portion 22 is configured to partition the inside of the housing 2. This partition portion 22 is located between the barrel accommodating portion 21 and the plunger accommodating portion 20. As shown in FIG. 1, the partition portion 22 is a ring-shaped member. The partition portion 22 is configured to protrude radially inward from the inner surface of the large-cylinder-side barrel accommodating portion 210 of the barrel accommodating portion 21 and the inner surface of the plunger accommodating portion 20. Therefore, one surface of the partition portion 22 defines the tip surface in the plunger accommodating portion 20, and the other surface defines the base end surface in the barrel accommodating portion 21. The partition portion 22 also includes a through hole 220 that passes the plunger 12 through the barrel accommodating portion 21 and the plunger accommodating portion 20. The through hole 220 is formed smaller than the barrel accommodating portion 21 and the plunger accommodating portion 20. The partition portion 22 of this embodiment is formed in the housing 2 in an inner flange shape. 1, the partition portion 22 is capable of coming into contact with the base end surface of the barrel 11 within the barrel accommodating portion 21. Thus, the partition portion 22 restricts the movement of the barrel 11 on the base end side.

[0027] The barrel biasing part B biases the barrel 11 from one side of the housing 2 toward the partition part 22. This barrel biasing part B is disposed in the barrel accommodating part 21. In this embodiment, the barrel biasing part B is configured by a compression coil spring wound around the central axis O. Specifically, as shown in FIG. 1, the barrel biasing part B is a coil spring through which the barrel 11 can be inserted. In addition, in the direction of the central axis O, one end side of the barrel biasing part B abuts against the barrel 11, and the other end side abuts against the biasing base part 211a. Specifically, one end side of the barrel biasing part B abuts against the tip side side of the cover part 111 of the barrel 11. Therefore, when the barrel 11 moves away from the partition part 22 toward the tip side of the barrel accommodating part 21, the barrel biasing part B is compressed between the barrel 11 and the biasing base part 211a. Therefore, the barrel biasing portion B biases the barrel 11 toward the partition portion 22 (the base end side). Note that the biasing force of the barrel biasing portion B in this embodiment is set to be weaker than the biasing force of the plunger biasing portion A.

[0028] The injection device 1 of this embodiment includes a trigger portion 23 configured to release the bias of the plunger biasing portion A. When the barrel 11 hits the partition portion 22 by the biasing force of the barrel biasing portion B, and the plunger 12 resists the biasing force of the plunger biasing portion A and the tip of the plunger 12 is located at the starting position, the trigger portion 23 can be locked so as not to release the bias of the plunger biasing portion A. That is, the trigger portion 23 has a biasing force holding position that holds the bias of the plunger biasing portion A so as not to release it. The trigger portion 23 releases the lock by a predetermined operation. That is, the trigger portion 23 moves from the biasing force holding position to the biasing force release position by a predetermined operation. As shown in FIG. 1, the trigger portion 23 includes a trigger mounting portion 230 provided at the base end of the plunger housing portion 20, a trigger main body portion 232 operated by the user, and a trigger lock operation portion 231 that locks the trigger main body portion 232 so that the user cannot operate it. The trigger attachment portion 230 is provided at the base end portion of the plunger accommodating portion 20. The trigger attachment portion 230 includes a base end portion 230A of the plunger accommodating portion 20 and a cylindrical portion 230B protruding from the base end portion 230A toward the base end side in the direction of the central axis O.

[0029] The base end 230A is formed with an insertion hole 200b centered on the central axis O. The base end 230A has a hook 230a on its base end side that engages with the trigger locking portion C5 of the engagement member C inserted into the insertion hole 200b. In this embodiment, the base end 230A also serves as the biasing base portion 200.

[0030] The cylindrical portion 230B has a cylindrical shape formed around the central axis O. The cylindrical portion 230B includes a cylindrical body portion 230BA provided so as to surround the hook portion 230a, a lock step portion 230BB protruding radially inward from the inner surface of the cylindrical body portion 230BA, and a protrusion portion 230BC protruding radially outward from the outer surface of the cylindrical body portion 230BA. The lock step portion 230BB is a step portion that restricts the operation of the trigger main body portion 232. Specifically, the lock step portion 230BB restricts the movement of the trigger main body portion 232 toward the tip side so that the trigger main body portion 232 (outer skirt portion 232b) cannot be pushed toward the tip side in the initial state (state before operation) of Figs. 1 and 10.

[0031] The protrusion 230BC guides the rotational operation of the trigger lock operation portion 231. The lock step portions 230BB and the protrusions 230BC are each provided in pairs so as to face each other in the diametrical direction of the cylindrical portion 230BA.

[0032] The trigger body 232 is pushed from the base end side to the tip end side in the direction of the central axis O by the user of the injection device 1, thereby starting the injection action by the injection device 1. The trigger body 232 includes a top plate 232a pressed by the user, an outer skirt 232b hanging down from the outer periphery of the top plate 232a to the tip end side, an inner skirt 232c hanging down from the top plate 232a inside the outer skirt 232b, and a flat plate 232d hanging down from the top plate 232a inside the inner skirt 232c. The top plate 232a is in the shape of a disk centered on the central axis O. The surface on the base end side of the top plate 232a is flat so that the user can easily press it.

[0033] The outer skirt portion 232b is formed into a cylindrical shape extending over the entire circumference around the central axis O. As shown in Fig. 1, the outer skirt portion 232b is configured such that its tip portion comes into contact with the locking step portion 230BB of the trigger attachment portion 230. In other words, the tip portion of the outer skirt portion 232b and the locking step portion 230BB form a locking mechanism portion V for locking the operation of the trigger portion 23.

[0034] As shown in Fig. 12, the outer skirt portion 232b is formed with a release groove 232ba that is open at the tip of the outer skirt portion 232b. This release groove 232ba is aligned along the central axis O. The lock step portion 230BB can be inserted into the release groove 232ba. Therefore, when the release groove 232ba and the lock step portion 230BB are aligned in the circumferential direction, the lock by the lock mechanism portion V is released as shown in Fig. 12. Therefore, the trigger body 232 can be pressed.

[0035] 1, an interlocking groove 230bb that is closed at the tip of the outer skirt portion 232b is formed in the outer skirt portion 232b. This interlocking groove 230bb is aligned along the central axis O. An interlocking protrusion 231ba of the trigger lock operation portion 231 fits into the interlocking groove 230bb. This causes the trigger main body 232 and the trigger lock operation portion 231 to rotate together around the central axis O.

[0036] The inner skirt portion 232c is formed in a cylindrical shape formed around the entire circumference of the central axis O. The inner diameter of the inner skirt portion 232c is approximately the same as the inner diameter of the insertion hole 200b at the base end. When the trigger body portion 232 is pushed in, the inner skirt portion 232c is pushed in so as to abut against the hook portion 230a at the base end portion 230A. This releases the engagement of the trigger engagement portion C5 (described later) that is engaged with the hook portion 230a. In other words, the inner skirt portion 232c functions as a trigger activation portion that activates the injection action.

[0037] The flat plate portion 232d is formed in a plate shape having a length in the direction of the central axis O and a width and thickness in the direction perpendicular to the length. The flat plate portion 232d is longer than the outer skirt portion 232b and the inner skirt portion 232c. The flat plate portion 232d has a width substantially equal to the width between the pair of trigger locking portions C5.

[0038] The trigger lock operation portion 231 is a member that is operated to release the lock of the trigger portion 23 that is in a locked state. As shown in Fig. 2, the trigger lock operation portion 231 includes a cylindrical main body portion 231a formed around a central axis O, and an inner flange portion 231b that extends radially inward from a base end portion of the cylindrical main body portion 231a in the direction of the central axis O. The cylindrical main body portion 231a is configured to rotatably surround the periphery of the trigger attachment portion 230.

[0039] A rotation groove 231aa extending along the circumferential direction is formed in the cylindrical main body portion 231a. The rotation groove 231aa is formed so that the protrusion 230BC of the trigger attachment portion 230 can be fitted into the rotation groove 231aa. The rotation angle of the trigger lock operation portion 231 is regulated by abutting both circumferential ends of the rotation groove 231aa against the protrusion 230BC.

[0040] The inner flange 231b is formed around the entire circumference of the cylindrical body 231a. The inner flange 231b has an interlocking protrusion 231ba that protrudes radially inward from the inner circumferential end. The interlocking protrusion 231ba is fitted into the interlocking groove 230bb. This causes the trigger lock operation part 231 and the trigger body 232 to rotate together. In this embodiment, a plurality of interlocking protrusions 231ba are provided. As shown in FIG. 12, the interlocking protrusion 231ba is also fitted into the release groove 232ba.

[0041] In such a trigger section 23, the trigger body 232 is installed inside the trigger mounting section 230. The trigger lock operation section 231 is installed outside the trigger mounting section 230 so as to move in conjunction with the trigger body 232. Specifically, as shown in FIG. 1, in the initial state (locked state before use), the tip of the outer skirt section 232b of the trigger body 232 abuts against the lock step section 230BB. The inner skirt section 232c is spaced away from the hook section 230a toward the base end side in the direction of the central axis O. The flat plate section 232d is inserted between the pair of trigger locking sections C5 with the width direction aligned along the opposing direction of the pair of trigger locking sections C5. In this embodiment, the trigger body is arranged relative to the trigger mounting section 230 as described above.

[0042] In the trigger lock operation part 231, as shown in FIG. 2, the cylindrical main body part 231a surrounds the outside of the cylindrical body part 230BA. The convex part 230BC is fitted into the rotation groove 231aa. The interlocking convex part 231ba is fitted into the interlocking groove 230bb and the release groove 232ba. In this manner, the trigger lock operation part 231 is disposed relative to the trigger attachment part 230. When the trigger lock operation part 231 is rotated, the trigger main body part 232 rotates in conjunction with this. When the release groove 232ba rotates until it coincides with the lock step part 230BB in the circumferential direction, the lock mechanism part V is released. Specifically, the lock of the lock mechanism part V refers to the contact between the tip part of the outer skirt part 232b and the lock step part 230BB. This allows the trigger main body part 232 to be pushed in (see FIG. 12). At this time, the thickness direction of the flat plate portion 232d is oriented in the direction in which the pair of trigger locking portions C5 face each other, allowing the pair of trigger locking portions C5 to bend radially inward.

[0043] When the trigger body 232 is pushed in, the inner skirt 232c (trigger activation portion) approaches the hook 230a. The inner skirt 232c then comes into contact with the trigger lock C5 that is locked to the hook 230a, bending the trigger lock C5 radially inward. This releases the lock between the hook 230a and the trigger lock C5. This activates the injection action of the injection device 1.

[0044] As shown in FIG. 1, the syringe 10 includes a barrel 11 having an injection needle 13 at its tip, and a plunger 12 inserted into the barrel 11 so as to be movable back and forth between the base end of the barrel 11 and the injection needle 13. In this embodiment, the barrel 11 is housed in a barrel housing 21. The barrel 11 includes a barrel body 110 filled with a drug solution, and a cover part 111 attached to the barrel body 110. The barrel body 110 of this embodiment includes a cylindrical main body part 110b and an outer flange part 110a protruding radially outward from the base end of the main body part 110b. The cover part 111 is attached to the barrel body 110 so as to cover the outer flange part 110a of the barrel body 110. Specifically, the cover part 111 is formed in a cylindrical shape with a part of the outer circumferential surface cut out and a bottom surface formed in a C-shape. The cover part 111 of this embodiment is formed to be larger in the radial direction than the outer flange of the barrel body 110. Therefore, the outer flange part 110a of the barrel body 110 is slid and inserted from the side of the cover part 111 so as to hold the barrel body 110 having a cylindrical C-shaped bottom surface. As a result, the cover part 111 is attached to the barrel body 110.

[0045] 3, the cover portion 111 is formed with an insertion hole 111e for inserting the plunger 12 into the barrel 11. The insertion hole 111e is provided in a circular shape on the upper surface of the cover portion 111. The insertion hole 111e is formed so as to be continuous with an opening of the cylindrical barrel body 110 when the cover portion 111 is attached to the barrel body 110. The insertion hole 111e in this embodiment is formed to be larger than a rod 120 described later and smaller than the opening of the barrel body 110.

[0046] As shown in FIG. 1 and FIG. 3, the barrel 11 is provided with a rotating engaged portion 111a. The rotating engaged portion 111a engages with a rotating engaging portion 120d, which will be described later, when the plunger 12, which will be described later, moves from the starting point to just before reaching the end point. Thus, the rotating engaged portion 111a is configured to rotate the plunger 12 around the central axis O. Specifically, the rotating engaged portion 111a is an inclined portion 111a having an inclined surface 111aa that guides the plunger 12 to rotate around the central axis O, a horizontal surface 111ab that extends horizontally from the inclined surface 111aa, and a vertical surface 111ac that extends from the horizontal surface 111ab in the direction of the central axis O. The inclined surface 111aa of the inclined portion 111a is disposed on the upper surface of the cover portion 111 attached to the barrel main body 110, as shown in FIG. 3. The inclined surface 111aa is inclined so as to slide when the rotary engagement portion 120d engages with it. The inclined surface 111aa is a surface against which the rotary engagement portion 120d approaching from the base end side in the direction of the central axis O abuts. The inclined surface 111aa is a spiral inclined surface 111aa that wraps around the central axis O and is inclined toward the tip side of the central axis O. The distance between the horizontal surface 111ab and the upper surface of the cover portion 111 is approximately equal to the distance between the tip surface and the base end surface of the partition portion 22. As shown in FIG. 3, the inclined portion 111a is formed around a circular insertion hole 111e formed in the cover portion 111. The inclined portion 111a is formed so as to enter the through hole 220 of the partition portion 22 when the barrel 11 abuts against the partition portion 22. In this embodiment, the inclined portion 111a functions as an engagement release mechanism Z1 that releases the engagement between the plunger 12 and the engagement member C. In this embodiment, a pair of inclined portions 111a are formed along the circular insertion hole 111e.

[0047] As shown in FIG. 3, the cover portion 111 includes a holding recess 111b as a rotation holding mechanism X that holds the rotation engaged portion 111a so as not to rotate with respect to the barrel housing portion 21. The cover portion 111 also includes a rotation restricting portion W that restricts the plunger 12 from rotating around the central axis O to a predetermined distance in the direction of the central axis O when the plunger 12 is inserted into the barrel 11. In this embodiment, the cover portion 111 includes an axial movement groove portion 111c as the rotation restricting portion W. The holding recess 111b is formed in a direction along the central axis O on the outer circumferential surface of the cover portion 111 that is formed into a circular shape in a plan view. In this embodiment, a pair of holding recesses 111b is formed in the X direction shown in FIG. 4 among the radial directions of the cover portion 111 that are perpendicular to the direction of the central axis O.

[0048] 3, the axial movement groove portion 111c is formed by cutting out the inner circumferential surface of the insertion hole 111e in the direction of the central axis O, and an axial movement protrusion 120e of the rod 120 described later is inserted into the axial movement groove portion 111c. In the present embodiment, the cover portion 111 is formed with two axial movement groove portions 111c.

[0049] As shown in FIG. 1, the plunger 12 includes a piston 121 (not shown in FIG. 1) that reciprocates between a start point and an end point while being in liquid-tight contact with the inside of the barrel 11, and a rod 120 that engages with the piston 121. In order to prevent the liquid medicine from leaking out of the barrel 11, the piston 121 is disposed so as to seal the inside of the barrel 11, as shown in FIG. 3 and FIG. 5. The piston 121 is also engaged with a rod 120, which will be described later. Specifically, as shown in FIG. 5, the piston 121 includes a connection hole 121a into which a tip projection 120h of the rod 120 is inserted, and a spiral annular projection 121b formed along the circumferential surface within the connection hole 121a. In this embodiment, the piston 121 is larger than an insertion hole 111e provided in the cover portion 111, so there is no risk of the piston 121 falling out of the barrel 11.

[0050] As shown in FIG. 1, the rod 120 is formed so as to extend along the central axis O in the housing 2. One side (tip side) of the rod 120 in the direction of the central axis O is engaged with a piston 121 (not shown in FIG. 1) in the barrel 11, and the other side (base end side) is engaged with an engagement member C. As shown in FIG. 3, the rod 120 includes a rod main body 120a extending in the direction of the central axis O, a pin portion 120b provided on the rod main body 120a, a first branch portion 120c engaged with the engagement member C, a second branch portion 120d for rotating the plunger 12, an axial movement protrusion 120e for preventing the plunger 12 from rotating around the central axis O, a retaining portion 120f for preventing the plunger 12 from coming off the barrel 11, and a tip protrusion 120h inserted into the piston 121. The rod main body 120a is formed in a cylindrical shape. The rod main body 120a is formed to have approximately the same size in the radial direction as the insertion hole 111e formed in the cover portion 111. In this embodiment, the rod main body 120a is formed to be longer than the barrel main body 110 of the barrel 11 in the direction of the central axis O so that the base end side of the plunger 12 extends outside the barrel 11 when the plunger 12 is inserted to the end point.

[0051] The pin portion 120b provided on the rod main body 120a engages the plunger 12 with the engagement member C. Specifically, in the injection device 1 shown in FIG. 1, the pin portion 120b is inserted into a release hole C30 (not shown in FIG. 1) of the engagement member C. The pin portion 120b is also arranged at a position that does not coincide with the release hole C30 in the circumferential direction. This prevents the plunger 12 from coming off the engagement member C, and maintains the engagement between the engagement member C and the plunger 12. In this embodiment, the pin portion 120b is formed so as to protrude from the base end of the rod main body 120a in a direction perpendicular to the central axis O (specifically, in the X direction) as shown in FIG. 3. In this embodiment, the pin portion 120b functions as a rotation prevention fitting portion 120b that fits with a rotation prevention fitting portion C20 described later. When the plunger 12 is inserted into the barrel 11 to form the syringe 10, the pin portions 120b are arranged in pair so as to face each other in the X direction, as shown in FIGS.

[0052] As shown in FIG. 3, the first branch portion 120c protrudes from the outer circumferential surface of the cylindrical rod main body 120a. The first branch portion 120c is provided on the base end side of the rod main body 120a in the direction of the central axis O. The first branch portion 120c is disposed on the tip end side of the pin portion 120b. Specifically, as shown in FIG. 1, when the pin portion 120b at the base end of the plunger 12 is inserted into and engaged with the engagement member C, the first branch portion 120c abuts against the biasing engagement portion C3 of the engagement member C so as to sandwich it between the pin portion 120b. This causes the plunger 12 to engage with the engagement member C. Therefore, the first branch portion 120c of this embodiment functions as a biased engaged portion 120c that engages with the biasing engagement portion C3. The first branch portion 120c is located on the bottom side (tip side) of the engagement member C as shown in FIG. 1, and restricts the plunger 12 from moving toward the engagement member C. In this embodiment, as shown in FIGS. 4 and 5, a pair of first branch portions 120c are provided in the X direction.

[0053] As shown in FIG. 3, the second branch 120d is provided on the tip side of the first branch 120c in the direction of the central axis O. The second branch 120d is a rotational engagement portion 120d provided on the plunger 12. The second branch 120d functions as an engagement release mechanism Z1 that releases the engagement between the plunger 12 and the engagement member C. When the plunger 12 moves from a position (starting point) on the tip side of the base end of the barrel 11 to just before reaching the tip (end point) of the barrel 11, the second branch 120d engages with an inclined portion (rotationally engaged portion) 111a provided on the cover portion 111. This causes the rod 120 to rotate around the central axis O. Therefore, when the plunger 12 and the barrel 11 are connected to form the syringe 10, the second branch 120d is disposed so as to face the inclined portion 111a in the direction of the central axis O. In addition, the second branch portion 120d of this embodiment is formed in a circular protrusion shape so as to be easily rotated along the inclined portion 111a. Furthermore, as shown in Figs. 4 and 5, the second branch portion 120d is provided in a pair in the X direction.

[0054] The axial movement protrusion 120e functions as a rotation restriction part W that restricts the plunger 12 inserted into the barrel 11 from rotating around the central axis O. Specifically, the axial movement protrusion 120e is inserted into the barrel 11 along the axial movement groove part 111c provided in the cover part 111. This restricts the rod 120 from rotating in the circumferential direction and allows it to move in the direction of the central axis O. The axial movement protrusion 120e protrudes from the outer circumferential surface of the rod main body 120a. Furthermore, the axial movement protrusion 120e extends from the tip of the rod main body 120a toward the base end side and extends to a position on the tip side of the second branch part 120d. In other words, the axial movement protrusion 120e extends continuously to the tip of the rod main body 120a at a predetermined distance from the second branch part 120d toward the tip side. When the rod 120 is inserted into the cover portion 111, the axial movement protrusion 120e fits into the axial movement groove portion 111c as shown in Fig. 4. In this embodiment, the axial movement protrusions 120e are provided in a pair in the Y direction.

[0055] The retaining portion 120f functions to prevent the rod 120 inserted into the barrel body 110 from being removed from the barrel body 110. The retaining portion 120f is formed to protrude from the outer circumferential surface of the rod body 120a. The protruding width of the retaining portion 120f is smaller than that of the second branch portion 120d. Specifically, the retaining portion 120f protrudes in a tapered shape in which the protruding width increases from the tip side to the base end side. In addition, the base end side surface of the retaining portion 120f is a surface perpendicular to the central axis O. Therefore, the plunger 12 is easily inserted into the barrel 11. In addition, the retaining portion 120f is provided on the tip side of the rod body 120a relative to the second branch portion 120d. Specifically, the retaining portion 120f is disposed between the tip and base end of the axial movement protrusion 120e. Therefore, when the rod body 120a is inserted into the cover part 111 so that the axial movement protrusion 120e as the rotation restricting part W is aligned with the axial movement groove part 111c of the cover part 111 as shown in FIG. 3, the retaining part 120f is inserted into the barrel 11 by climbing over the insertion hole 111e formed in the cover part 111 as shown in FIG. 5. When a force is applied to pull the rod 120 out of the barrel 11, the base end side surface of the retaining part 120f comes into contact with the bottom surface of the cover part 111 to prevent it from coming out. In addition, when the cap K described later is removed from the housing 2, the barrel 11 also advances toward the tip side due to the close contact between the needle cap K2 and the barrel 11. However, the advancement of the barrel 11 is prevented by the abutment between the retaining part 120f and the cover part 111. In this embodiment, the retaining part 120f is provided in a pair in the X direction as shown in FIG. 5.

[0056] The tip projection 120h engages the rod 120 with the piston 121. The tip projection 120h projects from the tip of the rod main body 120a toward the tip side in the direction of the central axis O. The tip projection 120h is formed smaller than the rod main body 120a so as to be insertable into the connecting hole 121a of the piston 121. When the rod 120 is inserted into the barrel main body 110, the tip projection 120h is inserted into the connecting hole 121a of the piston 121 as shown in FIG.

[0057] The engagement member C is disposed in the plunger accommodating portion 20 and engaged with the plunger 12, as shown in FIG. 1. As shown in FIG. 6, the engagement member C includes a cylindrically formed engagement body C1, a trigger locking portion C5 that is locked to a trigger portion 23 provided on the housing 2, a biasing receiving portion C2 that receives a bias from the plunger biasing portion A, and a biasing engagement portion C3 that is formed on one side (the tip side) of the biasing receiving portion C2 in the direction of the central axis O. The engagement body C1 is formed in a cylindrical shape so that the rod 120 is inserted when the engagement between the plunger 12 and the engagement member C is released. The engagement body C1 is formed in a cylindrical shape larger than the rod 120. The engagement body C1 is provided with an open passage C11 that penetrates the engagement member C in the radial direction. The open passage C11 is provided between the biasing receiving portion C2 and the biasing engagement portion C3, as shown in FIG. 6. Specifically, the open passage C11 is provided so as to cut out a portion between the biasing force receiving portion C2 and the biasing force engaging portion C3.

[0058] The trigger locking portion C5 protrudes from the other side (base end side) in the direction of the central axis O of the engagement body C1. The trigger locking portion C5 in this embodiment is formed in a bifurcated shape as shown in Fig. 6. A tapered rib C50 is formed at the protruding tip of the trigger locking portion C5, which becomes larger outward as it moves from the protruding tip to the protruding base end.

[0059] The biasing portion C2 is formed to protrude from the outer peripheral surface of the engagement body C1. In FIG. 1, the biasing portion C2 is abutted against the other end of the plunger biasing portion A. Therefore, the engagement member C approaches the biasing base portion 200 on the base end side of the central axis O, thereby compressing the plunger biasing portion A. In addition, the biasing portion C2 in this embodiment is formed in an outer flange shape (in this embodiment, a round outer flange shape) protruding radially outward from the engagement body C1. The biasing portion C2 is formed to have approximately the same size as the inner diameter of the cylindrical plunger accommodating portion 20 in the radial direction.

[0060] The engaging member C has a biasing engaging portion C3 that engages with the plunger 12 at the tip end of the biasing receiving portion C2 in the direction of the central axis O. The biasing engaging portion C3 has an outer flange shape that protrudes radially from the outer circumferential surface of the engaging body C1. In this embodiment, the biasing engaging portion C3 has a round outer flange shape.

[0061] The engagement member C is provided with a release hole C30 and a rotation prevention fitted portion C20 that fits with the rotation prevention fitting portion 120b. The release hole C30 is formed to penetrate the biasing engagement portion C3 in the direction of the central axis O, as shown in FIG. 8. The release hole C30 is formed to be continuous with the opening passage C11 in the circumferential direction, as shown in FIG. 7. The release hole C30 is formed larger than the pin portion 120b and the first branch portion 120c. Therefore, the base end portion of the rod 120 can be inserted into the engagement member C by passing the pin portion 120b through the release hole C30. In addition, as shown in FIG. 7, two release holes C30 of this embodiment are formed at positions facing each other in the radial direction. The release hole C30 is formed in a radial direction different from the holding recess C4 described later. Specifically, the release hole C30 is formed in a radial direction different from the first holding recess C40.

[0062] The rotation prevention fitted portion C20 is provided inside the bias receiving portion C2 of the engagement member C. Specifically, the rotation prevention fitted portion C20 is provided on the base end side in the direction of the central axis O from the bias receiving portion C2 as shown in FIG. 8. The rotation prevention fitted portion C20 of this embodiment is formed as a pin hole portion C20 into which the pin portion 120b provided at the base end of the rod 120 is inserted. Two pin hole portions C20 of this embodiment are provided in the engagement member C. The rotation prevention fitted portion C20 is located on the base end side in the direction of the central axis O from the release hole C30, but its radial position coincides with the release hole C30 as shown in FIG. 8. That is, the rotation prevention fitted portion C20 and the release hole C30 communicate with each other when viewed in the direction of the central axis O.

[0063] The engaging member C is formed with an engagement holding mechanism Y1 that holds the engaging member C so as not to rotate with respect to the plunger accommodating portion 20. Specifically, as shown in FIG. 6, the engaging member C is provided with a holding recess C4 that functions as the engagement holding mechanism Y1 in the urging receiving portion C2 and the urging engaging portion C3. When the engaging member C is inserted into the plunger accommodating portion 20, the holding recess C4 is engaged with the holding protrusion 201 of the plunger accommodating portion 20 by projection and recess. In this embodiment, the holding recess C4 is provided in four portions at 90° intervals in the substantially cylindrical engaging member C as shown in FIG. 7. The holding recess C4 includes a pair of first holding recesses C40 formed to face each other in the A direction shown in FIG. 7, and a pair of second holding recesses C41 formed to face each other in the B direction. In this embodiment, the first holding recesses C40 have a smaller circumferential width than the second holding recesses C41. Specifically, the pair of first holding recesses C40 are engaged with the pair of first holding protrusions 201a by projection and recess. Further, the pair of second retaining recesses C41 are recess-projected and fitted into the pair of second retaining protrusions C42. This allows the engagement member C and the plunger accommodating portion 20 to be aligned in the circumferential direction when the engagement member C is inserted into the plunger accommodating portion 20.

[0064] When assembling the injection device 1 in the initial state of this embodiment, first, as shown in FIG. 9, the plunger housing 20, the plunger biasing part A, the engagement member C, the partition part 22, the rod 120, the syringe 10, the barrel biasing part B, the barrel housing 21, and the cap K are arranged in the direction of the central axis O. Specifically, for the syringe 10, a needle cap K2 is attached to the tip of the barrel 11 so as to cover the injection needle 13, and then the piston 121 is inserted into the barrel body 110 filled with the drug solution so as to be located at the starting point, and a cover part 111 is attached to the barrel body 110 to form a prefilled syringe. The cap K is configured to cover the tip of the barrel housing 21, and serves to protect the injection needle 13 housed in the barrel housing 21. Then, the plunger biasing part A is housed in the plunger housing 20 along the direction of the central axis O, and then the engagement member C is inserted into the plunger housing 20. Here, the engagement member C is inserted so that the holding recess C4 of the engagement member C fits into the holding protrusion 201 in the plunger accommodating portion 20. At this time, the trigger lock operation portion 231 and the trigger main body portion 232 are rotated around the central axis O relative to the trigger mounting portion 230. This releases the lock of the lock mechanism portion V. In this embodiment, as shown in FIG. 9, the engagement member C is advanced into the plunger accommodating portion 20 with the first holding recess C40 disposed to face the front. The engagement recess C4 and the holding protrusion 201 are engaged to form an engagement holding mechanism Y1 that holds the engagement member C so as not to rotate around the central axis O relative to the plunger accommodating portion 20. When the engagement member C is advanced into the plunger accommodating portion 20, the other end side of the plunger urging portion A, one end of which is engaged with the urging base portion 200, is advanced toward the base end side of the plunger accommodating portion 20 while resisting the urging of the plunger urging portion A with the urging receiving portion C2 of the engagement member C. Thereafter, the trigger locking portion C5 is inserted into the insertion hole 200b defined by the biasing base portion 200. Then, the rib C50 of the trigger locking portion C5 is hooked onto the hook portion 230a, and the engagement member C is fixed to the trigger portion 23. This keeps the bias of the compressed plunger biasing portion A from being released. Therefore, the trigger portion 23 is in the biasing holding position. Thereafter, the trigger lock operating portion 231 and the trigger main body portion 232 are rotated, and the operation of the trigger portion 23 is locked by the locking mechanism portion V.Then, the rod 120 is engaged with the engaging member C accommodated in the plunger accommodating portion 20. Specifically, as shown in FIG. 8, the direction of the release hole C30 provided in the biasing engaging portion C3 is aligned with the direction in which the pin portion 120b is formed (specifically, the X direction). Then, the rod 120 is inserted into the engaging body C1 so that the pin portion 120b is inserted into the release hole C30. Then, the rod 120 or the engaging body C1 is rotated around the central axis O to make the direction of the release hole C30 different from the X direction as shown in FIG. 11. Also, the biasing engaging portion C3 is disposed between the pin portion 120b and the first branch portion 120c. This causes the rod 120 and the engaging member C to engage with each other as shown in FIG. 1 and FIG. 10. In this engaged state, the engaging member C and the rod 120 are engaged to move in conjunction with each other in the direction of the central axis O. Also, the engaging member C and the rod 120 are in a state in which they can rotate relatively around the central axis O.

[0065] Next, the barrel urging part B is housed in the barrel accommodating part 21 so that the other end of the barrel urging part B abuts against the urging base part 211a. Thereafter, the syringe 10 is inserted into the barrel accommodating part 21. When the syringe 10 is inserted into the barrel accommodating part 21, the holding recess 111b of the cover part 111 attached to the barrel body 110 of the syringe 10 fits into the holding protrusion 210b of the barrel accommodating part 21. Then, by fitting the holding recess 111b into the holding protrusion 210b, a rotation holding mechanism X is formed that holds the rotation engaged part (inclined part) 111a of the cover part 111 so as not to rotate around the central axis O with respect to the barrel accommodating part 21. Furthermore, after the partition part 22 is attached to the base end of the barrel housing part 21, a pair of outer peripheral surface protrusions (not shown) that are provided on the outer peripheral surface of the base end side of the barrel housing part 21 so as to extend in the direction of the central axis O and face each other in the radial direction of the barrel housing part 21 extend from the tip of the plunger housing part 20 to the base end side, penetrate the peripheral surface of the plunger housing part 20, and are fitted into a pair of axial cut parts 20a that face each other in the radial direction of the plunger housing part 20. As a result, the large cylinder side barrel housing part 210 is inserted into the plunger housing part 20, and the barrel housing part 21 and the plunger housing part 20 are engaged with each other. In this state, the barrel 11 abuts against the partition part 22 due to the biasing force of the barrel biasing part B. Then, the injection needle 13 on the tip side is housed in the barrel housing part 21, and the barrel 11 is in the first position. Here, when the barrel housing portion 21 and the plunger housing portion 20 are engaged with each other, the rod 120 housed in the plunger housing portion 20 is inserted into the barrel 11. Here, in this embodiment, the axial movement protrusion 120e and the axial movement groove portion 111c are fitted together to form a rotation restriction portion W that restricts the rotation of the plunger 12 around the central axis O relative to the barrel 11. Also, the second branch portion 120d as the rotation engagement portion 120d of the plunger 12 and the rotation engaged portion 111a of the barrel 11 are aligned in the direction of the central axis O. Specifically, as shown in FIG. 4, the second branch portion 120d and the rotation engaged portion 111a are arranged so as to overlap in the X direction. Therefore, when the plunger 12 is pushed from a position on the tip side of the base end of the barrel 11 toward the tip of the barrel 11, the plunger 12 moves in the direction of the central axis O while being rotationally restricted by the rotation restriction portion W.Then, when the plunger 12 reaches just before the tip of the barrel 11, the second branch portion 120d of the plunger 12 abuts against the inclined portion 111a of the barrel 11. That is, the rotation restricting portion W determines the engagement position between the second branch portion 120d (rotation engaging portion 120d) of the plunger 12 and the inclined portion 111a (rotation engaged portion 111a) of the barrel 11.

[0066] Thereafter, a cap K is attached to the tip side of the housing 2. The cap K closes the tip of the housing 2 and protects the injection needle 13 in the housing 2 from external factors. The cap K of this embodiment is formed larger than the housing 2 and is formed in a cylindrical shape so that the housing 2 can be inserted therein. The cap K is inserted into the housing 2 and includes a needle cap holding part K1 that is fitted around the injection needle 13. The needle cap holding part K1 is fitted with a needle cap K2 attached to the barrel 11 to be fitted around the injection needle 13. In this manner, the syringe 10 is inserted into the housing 2, and the injection device 1 in the initial state is assembled as shown in FIG. 10.

[0067] Next, a method of using the injection device 1 of this embodiment will be described. Figure 10 shows the initial state of the injection device 1 of this embodiment. In this state, a cap K is attached to the tip of the housing 2. Therefore, when using the injection device 1 of this embodiment, the cap K is first removed from the housing 2. This forms an opening at the tip of the housing 2 as shown in Figure 1. At this time, the needle cap K2 at the tip of the barrel 11 is removed together with the cap K while being fitted into the needle cap holding portion K1.

[0068] Next, as shown in FIG. 12, the injection needle 13 housed in the housing 2 is protruded from the opening at the tip of the housing 2. In this embodiment, as shown in FIG. 1, in the injection device 1 with the cap K removed, the injection needle 13 is housed in the housing 2, and the barrel 11 is in the first position. Therefore, the lock of the trigger part 23 is released, and the trigger part 23 is pushed into the plunger housing part 20. Specifically, the trigger lock operation part 231 and the trigger main body part 232 are rotated around the central axis O with respect to the trigger mounting part 230. As a result, the release groove 232ba of the trigger main body part 232 and the lock step part 230BB of the trigger mounting part 230 are aligned, and the lock of the trigger part 23 is released. In addition, the flat plate part 232d is rotated from the state shown in FIG. 10 so that the thickness is oriented in the direction in which the pair of trigger locking parts C5 face each other. Thereafter, the trigger main body part 232 is pushed toward the tip side in the direction of the central axis O. Then, the inner skirt portion 232c as the trigger activation portion abuts against the inclined surface at the tip of the trigger locking portion C5 of the engagement member C engaged with the hook portion 230a. Specifically, the inner skirt portion 232c abuts against the rib C50. As a result, the trigger locking portion C5, which is allowed to bend radially inward due to the rotation of the flat plate portion 232d, bends radially inward, and the engagement between the trigger locking portion C5 and the hook portion 230a is released. Therefore, as shown in FIG. 12, the engagement between the trigger portion 23 and the engagement member C is released. Therefore, the bias of the plunger biasing portion A, which has been held in a compressed state, is released. Therefore, the trigger portion 23 moves from the biasing holding position, which holds the biasing force of the plunger biasing portion A so as not to be released, to the biasing force releasing position, which releases the biasing force of the plunger biasing portion A.

[0069] The released plunger biasing portion A biases the biasing receiving portion C2. The engaging member C and the syringe 10 engaged with the engaging member C advance toward the tip side of the plunger housing portion 20. In the present embodiment, the barrel biasing portion B is set to have a weaker biasing force than the plunger biasing portion A. Therefore, as the engaging member C advances toward the tip side of the plunger housing portion 20, the barrel biasing portion B is pressed against the bottom surface of the cover portion 111 and compressed. The cover portion 111 moves in the direction of the central axis O along the holding convex portion 210b provided in the large barrel side barrel housing portion 210, with the holding concave portion 111b. The cover portion 111 moves until the bottom surface abuts against the barrel receiving portion 210a. Therefore, the barrel biasing portion B is compressed until the bottom surface of the cover portion 111 abuts against the barrel receiving portion 210a, as shown in FIG. 12. In addition, as the barrel 11 moves toward the tip side of the barrel housing portion 21, the injection needle 13 provided at the tip of the barrel body 110 protrudes from the barrel housing portion 21. Therefore, the barrel 11, which is in the first position, moves to the second position. When the engaging member C and the syringe 10 move, the engaging member C is restricted from rotating about the central axis O by the engaging and holding mechanism Y1. In addition, the rotation of the rotationally engaged part 111a is restricted from rotating about the central axis O by the rotating and holding mechanism X. Furthermore, the rotation of the plunger 12 is restricted from rotating about the central axis O by the rotation restricting part W. This prevents the engaging member C from being accidentally disengaged from the plunger 12. In addition, the engaging position of the rotationally engaged part 120d and the rotationally engaged part 111a is prevented from being displaced.

[0070] Next, when the cover portion 111 abuts against the barrel receiving portion 210a, the movement of the barrel 11 toward the tip side is restricted. On the other hand, the engagement member C and the plunger 12 move further toward the tip side in the direction of the central axis O due to the biasing force of the plunger biasing portion A. Thus, the plunger 12 advances inside the barrel 11. Here, the engagement member C moves toward the tip side of the plunger accommodating portion 20 so that the holding recess C4 is aligned with the holding protrusion 201 provided in the plunger accommodating portion 20. When the plunger 12 advances inside the barrel 11, as shown in FIG. 12, the axial movement protrusion 120e moves along the axial movement groove portion 111c provided in the cover portion 111. In other words, even when the plunger 12 is pushed into the barrel 11, the engagement member C is restricted from rotating around the central axis O by the engagement holding mechanism Y1. Moreover, the rotation of the rotationally engaged part 111a of the barrel 11 around the central axis O is restricted by the rotation holding mechanism X. Furthermore, the rotation of the plunger 12 (rotationally engaged part 120d) around the central axis O is restricted by the rotation restricting part W. Furthermore, when the plunger 12 advances into the barrel 11, the piston 121 engaged with the rod 120 advances inside the barrel body 110. Thus, the piston 121 pushes the liquid medicine out of the injection needle 13. Then, when the plunger 12 approaches the tip of the barrel 11, the axial movement protrusion 120e extending from the tip of the rod body 120a to the tip side beyond the second branch part 120d comes out of the axial movement groove part 111c to the tip side. Therefore, the restriction by the rotation restricting part W is released. That is, the plunger 12 (rotationally engaged part 120d) is allowed to rotate around the central axis O with respect to the rotationally engaged part 111a of the barrel 11. Then, as shown in FIG. 13, the second branch portion 120d as the rotation engaging portion comes into contact with the inclined portion 111a as the rotationally engaged portion, and the disengagement mechanism Z1 is activated.

[0071] The plunger 12 moves in the barrel 11 from a position (start point) on the tip side of the base end of the barrel 11 to the tip (end point) of the barrel 11 by the force generated by the plunger biasing part A. Then, after the plunger 12 reaches just before the tip of the barrel 11, the second branch part 120d slides along the inclined part 111a (specifically, the inclined surface 111aa). Therefore, as shown in FIG. 13, the state where the second branch part 120d and the inclined part 111a (specifically, the inclined surface 111aa) are in contact with each other changes to a state where the second branch part 120d slides along the inclined part 111a as shown in FIG. 14. Here, the engaging member C is restricted not to rotate by the engaging and holding mechanism Y1, and the rotation engaged part 111a is restricted to rotate by the rotating and holding mechanism X. On the other hand, the restriction by the rotation restricting part W that restricts the rotation of the plunger 12 is released. Therefore, the plunger 12 and the engaging member C rotate relatively around the central axis O. Specifically, in this embodiment, the plunger 12 rotates around the central axis O relative to the engaging member C. Also, the rotation engaging portion 120d of the plunger 12 rotates around the central axis O relative to the rotation engaged portion 111a. Specifically, the rotation engaging portion 120d rotates about 30° to the left in a state in which it engages with the inclined surface 111aa of the inclined portion 111a shown in FIG. 13. Therefore, the rotation engaging portion 120d moves to the upper surface side of the cover portion 111 shown in FIG. 14.

[0072] In addition, as shown in FIG. 14, the pin portion 120b and the first branch portion 120c also rotate due to the rotation of the plunger 12. Here, in the rod 120 of this embodiment, the pin portion 120b and the first branch portion 120c are arranged in the X direction. Therefore, as shown in FIG. 15, when the first branch portion 120c is arranged at a position that coincides with the release hole C30 in the circumferential direction due to the rotation of the plunger 12, the pin portion 120b is also arranged at a position that coincides with the release hole C30 in the circumferential direction. Therefore, the engagement release mechanism Z1 is actuated, and the engagement between the biased engagement portion C3 and the biased engaged portion 120c is released. As a result, the engagement between the plunger 12 and the engagement member C is released. At this time, the plunger 12 has reached the end point.

[0073] The engagement between the biasing engaging portion C3 and the biased engaged portion 120c is released, and thus the biasing force of the plunger biasing portion A against the syringe 10 is released. Therefore, the plunger biasing portion A pushes only the engaging member C toward the tip side. In response to this, the barrel biasing portion B compressed by the plunger biasing portion A is released. Therefore, the barrel biasing portion B pushes the syringe 10 toward the base end side. Therefore, as shown in FIG. 16, the engaging member C moves to a position where the biasing engaging portion C3 closely faces the partition portion 22 in a state where rotation is restricted by the engagement holding mechanism Y1, and is biased and fixed at this position. Also, in a state where the rotation engaged portion 111a is rotationally restricted by the rotation holding mechanism X, the barrel 11 (specifically, the cover portion 111) moves to a position where it closely faces the partition portion 22. Then, the barrel 11 is biased and fixed at this position. Here, one end side of the barrel biasing portion B is in contact with the bottom surface of the cover portion 111. Therefore, the cover portion 111 is pushed toward the partition portion 22 by the bias of the barrel biasing portion B. Then, in this embodiment, as shown in FIG. 16, when the barrel 11 is in contact with the bottom surface of the partition portion 22, the inclined portion 111a enters the through hole 220 of the partition portion 22. Furthermore, as the cover portion 111 is pushed toward the partition portion 22, the plunger 12 moves toward the base end side of the housing 2 together with the barrel 11. Therefore, the first branch portion 120c is inserted through the release hole C30 of the engagement member C, and as shown in FIG. 17, the pin portion 120b is fitted into the rotation prevention fitted portion C20. Therefore, the engagement between the rotation prevention fitted portion (pin portion) 120b and the rotation prevention fitted portion C20 prevents the plunger 12 from rotating in the reverse direction. This functions as a reverse rotation prevention mechanism Y2 that prevents the plunger 12 from rotating in a direction opposite to the rotation when the plunger 12 is released from engagement with the engagement member C. In this manner, when the disengagement mechanism Z1 operates, the engagement member C is biased and fixed in close proximity to the partition portion 22 while being restricted in rotation. In addition, a reverse rotation prevention mechanism Y2 is formed to prevent the plunger 12 from rotating in reverse relative to the engagement member C. Thus, a reverse rotation prevention means Y is formed that holds the disengaged plunger 12 so as not to rotate in reverse. The rotationally engaged portion 111a (cover portion 111) of the barrel 11 is biased and fixed in close proximity to the partition portion 22 while being restricted in rotation.In this way, the rotation of the engaging member C, the plunger 12, and the rotating engaged portion 111a after disengagement is restricted, thereby maintaining the disengaged state of the engaging member C and the plunger 12. Therefore, as shown in FIG. 16, the biased engaged portion (first branch portion) 120c is located between the biased engaging portion C3 and the biased receiving portion C2, which are adjacent to and facing the partition portion 22. In this way, after disengagement, the syringe 10 is biased and fixed at a position closer to the base end than the biased engaging portion C3 of the engaging member C by the biasing force toward the base end by the barrel biasing portion B. In addition, the biased engaging portion C3 of the engaging member C is biased and fixed at a position closer to the tip end than the biased engaged portion 120c by the biasing force toward the tip end by the plunger biasing portion A. In this way, the disengaged state of the engaging member C and the plunger 12 is maintained.

[0074] In this embodiment, the plunger 12 moves to the base end side of the housing 2, the first branch portion 120c passes through the release hole C30 of the engagement member C, and the pin portion 120b is fitted into the rotation prevention fitting portion C20. At this time, in the direction of the central axis O and the circumferential direction, the first branch portion 120c is disposed at the same position as the through hole 202 provided in the circumferential direction of the plunger housing portion 20. Therefore, the first branch portion 120c visible inside the housing 2 through the through hole 202 from the outside of the housing 2 functions as an indicator indicating that the drug administration has been completed. In this case, it is preferable that the first branch portion 120c has a different color from other members, for example, the rod main body 120a. This makes it possible to more reliably indicate that the drug administration has been completed.

[0075] The above is a description of the method of using the injection device 1 of this embodiment. The injection device 1 of this embodiment includes a syringe 10 including a barrel 11 with an injection needle 13 at its tip, a plunger 12 inserted into the barrel 11 so as to be capable of reciprocating between the base end side of the barrel 11 and the tip side, and a cylindrical housing 2 for accommodating the syringe 10, and has two positions on one side in the direction of a central axis O: a first position where the injection needle 13 is accommodated in the housing, and a second position where the injection needle 13 is protruding from one side of the housing 2 at a predetermined distance to one side from the first position. a housing 2 in which a barrel accommodating section 21 is formed to accommodate the barrel 11 so as to be movable between a first position where the injection needle 13 is inserted and a second position where the injection needle 13 is inserted, and a plunger accommodating section 20 is formed on the other side of the barrel accommodating section 21 to accommodate a plunger 12 protruding from the base end side of the barrel 11; a barrel biasing section B arranged in the barrel accommodating section 21 to bias the barrel 11 from one side of the housing 2 to the other side where the injection needle 13 is accommodated in the housing 2; The barrel 11 has an engaging member C that engages with the engaging member C, a plunger biasing section A that engages with the engaging member C and biases the plunger 12 from the starting point toward the end point, and a biasing force retaining position that retains the biasing force of the plunger biasing section A so as not to be released in a state in which the barrel 11 is held in a state in which the injection needle 13 is housed by the barrel biasing section B and the plunger 12 is held in a state in which the tip is located at the starting point position against the biasing force of the plunger biasing section A. and a trigger portion 23 configured to move from a biasing force release position to a biasing force release position where the biasing force is released, and as the trigger portion 23 moves to the biasing force release position, the plunger 12 moves from the start point to the end point by the biasing force of the plunger biasing portion A, and the plunger 12 and the engaging member C are rotated relatively around a central axis O, thereby releasing the engagement between the plunger 12 and the engaging member C and positioning the plunger 12 at the end point.

[0076] In the injection device 1 having the above-described configuration, when a predetermined operation is performed on the trigger portion 23, the bias of the plunger biasing portion A is released, and the bias of the plunger biasing portion A moves the syringe 10 to one side in the direction of the central axis O until the injection needle 13 protrudes from the housing 2. When the syringe 10 moves until the injection needle 13 protrudes from the housing 2, the bias of the barrel biasing portion B holds the barrel 11 in position against the bias of the plunger biasing portion A, while the plunger 12 continues to move to one side in the direction of the central axis O and is pushed into the barrel 11 by the bias of the plunger biasing portion A, and the medicinal liquid in the barrel 11 is dispensed. Then, when the plunger 12 moves to the end point, the dispense is completed. Here, in the injection device 1 of this embodiment, the disengagement mechanism Z1 is configured to disengage the plunger 12, which has moved toward the end point, from the engaging member C by rotating them relative to each other, so that the biasing force applied to the plunger 12 by the plunger biasing part A is released by disengaging the plunger 12 from the engaging member C. Then, the syringe 10 is biased toward the other side in the direction of the central axis O by the biasing force of the barrel biasing part B, thereby drawing the injection needle 13 into the housing 2.

[0077] Specifically, according to the injection device 1 of this embodiment, the disengagement mechanism Z1 is configured to disengage the plunger 12, which has moved from the starting point to the end point, from the engaging member C by rotating the plunger 12 and the engaging member C relative to each other. Therefore, at the end point of the movement of the plunger 12, the engagement between the plunger 12 and the engaging member C is released, and the urging force of the plunger urging part A on the plunger 12 is released. Then, the syringe 10 is pushed to the other side in the direction of the central axis O by the urging force of the barrel urging part B. This allows the injection needle 13 to be retracted inside the housing 2.

[0078] In addition, in the injection device of this embodiment, the disengagement mechanism includes a rotational engagement portion provided on the plunger and a rotational engaged portion provided on the barrel, and is configured so that when the plunger moves from the starting point to the end point and the rotational engagement portion engages with the rotational engaged portion, the plunger rotates about the central axis and disengages the plunger from the engaging member.

[0079] Therefore, according to the injection device 1 having the above configuration, the engagement position between the rotation engaging portion 120d and the rotation engaged portion 111a can be set according to the movement position of the plunger 12 relative to the barrel 11, so that the engagement can be released according to the end point of the movement of the plunger 12. Specifically, when the plunger 12 moves from a position on the tip side of the base end of the barrel 11 to just before reaching the tip of the barrel 11, the second branch portion 120d engages with the inclined portion 111a, and the second branch portion 120d slides along the inclined portion 111a. As a result, the plunger 12 rotates around the central axis, and as shown in FIG. 15, the pin portion 120b and the first branch portion 120c are positioned at a position that coincides with the release hole C30 in the circumferential direction, and the engagement between the plunger 12 and the engagement member C is released. Then, the barrel biasing portion B pushes the cover portion 111 toward the partition portion 22. Therefore, as shown in FIG. 16, the plunger 12 is accommodated in the engagement member C, and the barrel 11 moves toward the partition portion 22. Therefore, the injection needle 13 can be retracted inside the housing 2.

[0080] According to the injection device 1 of this embodiment, the plunger 12 is inserted into the engaging member C. Therefore, after the plunger 12 is disengaged from the engaging member C, the biased engaged portion 120c is biased and fixed between the biased engaging portion C3 and the biased receiving portion C2, which are adjacent to and opposed to the partition portion 22. This prevents the biased engaging portion C3 and the biased engaged portion 120c from returning to the engaged state, thereby preventing the injection needle 13, which has been housed once, from erroneously protruding again.

[0081] According to the injection device 1 of this embodiment, the disengagement mechanism Z1 includes a rotational engagement portion 120d provided on the plunger 12 and a rotationally engaged portion 111a provided on the barrel 11, and is configured such that when the plunger 12 moves from the starting point to just before reaching the end point, the rotational engagement portion 120d engages with the rotationally engaged portion 111a, causing the plunger 12 to rotate around the central axis O and disengage the plunger 12 from the engaging member C. Therefore, the engagement position between the rotational engagement portion 120d and the rotationally engaged portion 111a can be set in accordance with the movement position of the plunger 12 relative to the barrel 11, so that the disengagement can be performed just before the end point of the movement of the plunger 12.

[0082] Moreover, the injection device 1 of this embodiment includes a rotation holding mechanism X that holds the rotation engaged part 111a so as not to rotate relative to the barrel housing part 21. The injection device 1 also includes a reverse rotation prevention means Y that holds the plunger 12, which has been released from engagement with the engagement member C when the engagement release mechanism Z1 is activated, so as not to rotate in reverse. Therefore, after the rotation engagement part 120d and the rotation engaged part 111a engage with each other, the plunger 12 rotates and is released from engagement with the engagement member C, and the plunger 12 can be prevented from rotating in reverse and becoming engaged again.

[0083] Furthermore, according to the injection device 1 of this embodiment, the reverse rotation prevention means Y includes an engagement holding mechanism Y1 that holds the engaging member C so as not to rotate relative to the plunger housing portion 20, and a reverse rotation prevention mechanism Y2 that holds the plunger 12 after disengagement so as not to rotate reversely relative to the engaging member C. Therefore, by preventing the rotation of the rotatable engaged portion 111a and the engaging member C and then preventing reverse rotation of the plunger 12 after disengagement, reverse rotation can be reliably prevented and the engagement state can be effectively prevented from being established again.

[0084] According to the injection device 1 of the present embodiment, the reverse rotation prevention mechanism Y2 includes a rotation prevention fitting portion 120b provided at the other end of the plunger 12 and a rotation prevention fitted portion C20 provided at the urging receiving portion C2 of the engagement member C, and is configured to prevent the plunger 12 from rotating in a reverse direction by disengaging the engagement portion C3 and the urging engaged portion 120c by the disengagement mechanism Z1, the engagement member C faces the partition portion 22 closely, and the urging engaged portion 120c is positioned between the urging engagement portion C3 and the urging receiving portion C2, and the rotation prevention fitting portion 120b and the rotation prevention fitted portion C20 are fitted together. Therefore, the rotation engaged portion 111a of the barrel 11 is prevented from rotating by the rotation holding mechanism X, and the engagement member C is prevented from rotating by the engagement holding mechanism Y1. The urging engaged portion 120c of the plunger 12 is positioned between the urging engagement portion C3 and the urging receiving portion C2 of the engagement member C. Furthermore, the anti-rotation fitting portion 120b and the anti-rotation fitted portion C20 are fitted together to prevent reverse rotation of the plunger 12. This reliably maintains the disengaged state between the plunger and the engaging member C, thereby preventing the injection needle 13 from protruding again.

[0085] As described above, according to this embodiment, the engagement between the plunger 12 and the engaging member C is released by rotating them relative to each other, which has the effect of enabling the injection needle to be reliably returned.

[0086] In addition, the injection device is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention. For example, other configurations can be added to the configurations of the above embodiment. In addition, part of the configurations of the above embodiment can be replaced with other configurations. Furthermore, part of the configurations of the above embodiment can be deleted.

[0087] In this embodiment, the disengagement mechanism Z1 rotates the plunger 12. However, this is not limited to the above, and the engaging member C may be rotated, or both the plunger 12 and the engaging member C may be rotated in opposite directions. In the case of rotating the engaging member C, for example, a rotational engaging portion may be provided on the engaging member C, and a rotationally engaged portion may be provided on the barrel or the housing. For example, as shown in FIG. 18, a holding protrusion C4 may be provided as a rotational engaging portion on the biasing engaging portion of the engaging member C, and as shown in FIG. 19, a holding recess 201 may be provided as a rotationally engaged portion on the plunger accommodating portion 20. In this case, the holding recess 201 provided on the plunger accommodating portion 20 is provided to rotate the engaging member C. Specifically, the holding recess 201 extending from the base end to the tip end side along the central axis O direction is inclined circumferentially and toward the tip end on the tip end side of the central axis O. This allows the engaging member C to rotate when the holding protrusion C4 of the engaging member C passes through the inclined tip end side holding recess 201. In this case, the plunger biasing portion may be formed of a torsion spring, for example. That is, when the engagement between the hook portion and the trigger locking portion is released and the plunger biasing portion is biased toward the tip side of the plunger housing portion, the biasing force moves the engagement member C toward the tip side of the plunger housing portion. Then, by utilizing the rotation of the plunger biasing portion formed of a torsion spring about the central axis O, the holding convex portion C4 of the engagement member C is passed through the inclined tip side holding recess 201. In this manner, the engagement member C may be rotated. When formed of a torsion spring, the tip side of the holding recess 201 may be a horizontal groove.

[0088] Next, an injection device according to a second embodiment, which is configured to rotate an engagement member by utilizing rotation about the central axis of a plunger biasing portion, will be described with reference to Figures 20 to 28. In the description of the injection device according to the second embodiment, the same reference numerals are used for configurations similar to those of the first embodiment, and the description of parts overlapping with the first embodiment will not be repeated, but only differences from the first embodiment will be described.

[0089] 20, the plunger accommodating portion 20 of the second embodiment includes a tip accommodating portion 20A and an accommodating body portion 20B disposed on the base end side of the tip accommodating portion 20A. Note that the plunger accommodating portion 20 of the second embodiment does not have a through hole 202 penetrating in the radial direction.

[0090] The tip accommodating portion 20A accommodates the base end of the barrel accommodating portion 21 and the partition portion 22. This tip accommodating portion 20A is disposed on the tip side of the plunger accommodating portion 20. The tip accommodating portion 20A is formed in a tubular shape (specifically, cylindrical shape). As shown in FIG. 20, the tip accommodating portion 20A includes an axial cutout portion 20a that continues from the tip to the base end side and penetrates the circumferential surface. The axial cutout portions 20a of the second embodiment are provided in a pair so as to face each other in the radial direction.

[0091] The accommodating body 20B accommodates the plunger biasing portion A and the engaging member C. The accommodating body 20B is formed in a tubular shape (specifically, a cylindrical shape). The accommodating body 20B is connected to the base end of the tip accommodating portion 20A. Therefore, the accommodating body 20B is disposed on the base end side of the plunger accommodating portion 20A. The accommodating body 20B is formed longer than the tip accommodating portion 20A in the central axis direction. Furthermore, the accommodating body 20B of the second embodiment has an inner diameter and an outer diameter smaller than the tip accommodating portion 20A. Therefore, the plunger accommodating portion 20 is formed such that the inner diameter and the outer diameter on the tip side are larger than the base side. In addition, the tip of the accommodating body 20B is provided in the plunger accommodating portion 20 as a step of the inner diameter difference between the tip accommodating portion 20A and the accommodating body 20B.

[0092] A biasing base 200 is provided on the base end side of the housing main body 20B. As shown in Fig. 20, the biasing base 200 of the second embodiment is provided with a biasing attachment 200c for attaching one end of the plunger biasing part A housed in the housing main body 20B. The biasing attachment 200c of the second embodiment is formed as an insertion hole 200c penetrating the biasing base 200 in the central axis direction so that one end of the plunger biasing part A can be inserted therethrough.

[0093] The plunger accommodating portion 20 includes a retaining protrusion 201 (specifically, a first retaining protrusion 201a and a second retaining protrusion 201b) as an engagement and retention mechanism Y1 that retains the engaging member C so as not to rotate relative to the plunger accommodating portion 20. As shown in FIG. 20, in the second embodiment, the retaining protrusion 201 is formed in the accommodating body portion 20B. The retaining protrusion 201 is continuously formed from the base end toward the tip end side of the accommodating body portion 20B. Therefore, the retaining protrusion 201 fits into a retaining recess C4 described later, so that the retaining protrusion 201 guides the engaging member C in the central axis direction in the plunger accommodating portion 20. Furthermore, the retaining protrusion 201 fits into the retaining recess C4, so that the rotation of the engaging member C is restricted, and the rotation by the plunger biasing portion A is restricted.

[0094] Unlike the first embodiment, the tip of the holding protrusion 201 in the second embodiment is provided on the base end side of the tip of the housing main body 20B formed as a step in the plunger housing 20. Therefore, the tip side of the housing main body 20B from the tip of the holding protrusion 201 is formed as a flat surface. In the second embodiment, the distance from the tip of the holding protrusion 201 to the tip of the housing main body 20B is equal to the distance from the bias receiving portion C2 to the bias engaging portion C3 of the engaging member C. In the second embodiment, the tips of the first holding protrusion 201a and the second holding protrusion 201b are arranged at the same position in the central axis direction as shown in FIG.

[0095] The plunger accommodating portion 20 of the second embodiment includes an engagement release mechanism Z1 that releases the engagement between the plunger 12 and the engaging member C. The plunger accommodating portion 20 of the second embodiment includes a rotationally engaged portion 201 as the engagement release mechanism Z1. Specifically, the accommodating main body portion 20B includes the rotationally engaged portion 201. In the second embodiment, the holding protrusion 201 functions as the rotationally engaged portion 201.

[0096] The plunger accommodating portion 20 is provided with a rotation allowing mechanism T that allows relative rotation around the central axis between the plunger accommodating portion 20 and the engaging member C. The accommodating body portion 20B of the second embodiment is provided with an accommodating protrusion 203 as the rotation allowing mechanism T. As shown in FIG. 20, the accommodating protrusion 203 extends continuously from the base end to the tip end of the accommodating body portion 20B. Therefore, the accommodating protrusion 203 is disposed on the tip side of the holding protrusion 201 in the accommodating body portion 20B. The accommodating protrusion 203 of the second embodiment is formed as a pair in the cylindrical accommodating body portion 20B so as to face each other in the radial direction. Furthermore, the accommodating protrusion 203 is disposed between the first holding protrusion 201a and the second holding protrusion 201b.

[0097] The accommodating main body 20B includes a rotation stopping mechanism U that stops the rotation of the plunger 12 and the engaging member C about the central axis. The accommodating main body 20B of the second embodiment includes an engaging stopped portion 203 as the rotation stopping mechanism U. The engaging stopped portion 203 is configured as an accommodating protrusion 203 that protrudes radially inward within the accommodating main body 20B.

[0098] In the trigger portion 23 of the second embodiment, the configurations of the trigger attachment portion 230 and the trigger body portion 232 are different from those of the first embodiment. Specifically, in the trigger attachment portion 230 of the second embodiment, as shown in FIG. 20, a biasing attachment portion 200c (specifically, an insertion hole 200c) for attaching one end of the plunger biasing portion A to the base end portion 230A is formed. Also, in the cylindrical body portion 230BA of the second embodiment, a one-side guide portion a1 communicating with the biasing attachment portion 200c is formed. In the second embodiment, the one-side guide portion a1 is formed to be recessed inside the cylindrical body portion 230BA so that one end of the plunger biasing portion A inserted into the insertion hole 200c fits thereto.

[0099] In the second embodiment, the trigger body 232 is formed with a second guide portion a2 along which one end of the plunger biasing portion A is aligned with the outer skirt portion 232b. The second guide portion a2 is formed so that the outer periphery of the outer skirt portion 232b is recessed. The second guide portion a2 is formed continuously from the tip side to the base end side of the outer skirt portion 232b. As shown in FIG. 20, in the second embodiment, when the trigger portion 23 is unlocked, the second guide portion a2 coincides with the one guide portion a1 in the circumferential direction and communicates with the one guide portion a1 in the central axis direction. Then, by pressing the trigger body 232, the second guide portion a2 overlaps with the one guide portion a1.

[0100] The plunger biasing portion A of the second embodiment is configured as a torsion spring that expands and contracts in the direction of the central axis and accumulates a force (circumferential biasing force) that rotates around the central axis. The plunger biasing portion A constitutes the disengagement mechanism Z1. Therefore, the disengagement mechanism Z1 rotates the engagement member C around the central axis by utilizing the circumferential biasing force of the plunger biasing portion A. One end of the plunger biasing portion A is attached to the biasing attachment portion 200c provided in the plunger accommodating portion 20 shown in FIG. 20. In addition, the other end of the plunger biasing portion A is attached to the biasing attachment portion C7 provided in the engagement member C shown in FIG. 22. Therefore, the plunger biasing portion A moves the engagement member C by expanding from a compressed state. In addition, the plunger biasing portion A configured as a torsion spring is configured to rotate the engagement member C around the central axis by the circumferential biasing force due to torsion. Therefore, the plunger biasing portion A is configured to bias the engaging member C in a direction to rotate the engaging member C about the central axis line. The plunger biasing portion A of the second embodiment rotates when the engagement between the holding convex portion 201 and the holding concave portion C4 is released and the restriction on rotation by the engaging holding mechanism Y1 is released.

[0101] The syringe 10 of the second embodiment differs from the first embodiment in that it does not include the disengagement mechanism Z1. Specifically, as shown in Fig. 21, in the second embodiment, the rod 120 is not provided with a second branch portion 120d as a rotational engagement portion. In addition, the cover portion 111 is not provided with a rotationally engaged portion. Therefore, the cover portion 111 of the second embodiment has a flat upper surface.

[0102] Also, the axial movement protrusion 120e of the second embodiment is formed longer toward the base end side of the rod 120 than in the first embodiment. That is, as shown in Fig. 21, the axial movement protrusion 120e of the second embodiment is set to a length that prevents the plunger 12 inserted into the barrel 11 from coming out of the axial movement groove 111c of the cover part 111 when the plunger 12 reaches the tip (end point) of the barrel 11. Therefore, in the second embodiment, rotation around the central axis of the rod 120 is prevented.

[0103] The engaging member C of the second embodiment is provided with a biasing attachment portion C7 for attaching the other end of the plunger biasing portion A. Specifically, as shown in FIG. 22, an insertion hole C7 for inserting the other end of the plunger biasing portion A is formed in the bias receiving portion C2 as the biasing attachment portion C7. Therefore, in the second embodiment, the engaging member C can rotate around the central axis by the circumferential biasing force of the plunger biasing portion A. Note that the biasing attachment portion C7 of the second embodiment is provided between the holding recess (specifically, the first holding recess C40) and the engaging recess C6 in the circumferential direction of the outer flange-shaped bias receiving portion C2. Therefore, in the second embodiment, when the engaging member C and the plunger biasing portion A are accommodated in the plunger accommodating portion 20, one end of the plunger biasing portion A is attached to the biasing attachment portion 200c, and the other end of the plunger biasing portion A is inserted into the insertion hole C7. Then, when a torque is applied to the plunger biasing portion A, the engaging member C advances toward the base end side of the plunger accommodating portion 20, whereby the plunger biasing portion A is compressed.

[0104] The engaging member C of the second embodiment includes a holding recess C4 as an engaging and holding mechanism Y1. When the engaging member C is housed in the plunger housing 20, the holding recess C4 fits into the holding protrusion 201. Specifically, in the second embodiment, as shown in FIG. 22, the circumferential surfaces of the urging receiving portion C2 and the urging engaging portion C3 are recessed to form the holding recess C4. The holding recess C4 is formed with a recess width that can fit into the holding protrusion 201. Therefore, when the engaging member C is housed in the plunger housing 20, the holding recess C4 fits into the holding protrusion 201, so that the engaging member C is restricted from rotating in the central axis direction. In addition, in the second embodiment, the engaging member C moves in the central axis direction while the holding recess C4 is aligned with the holding protrusion 201. As a result, the engaging member C is guided in the central axis direction within the plunger housing 20.

[0105] The engaging member C of the second embodiment includes a rotating engaging portion C4 as the disengagement mechanism Z1. Specifically, as shown in FIG. 22, in the engaging member C of the second embodiment, a holding recess C4 is formed as the rotating engaging portion C4 in the urging receiving portion C2 and the urging engaging portion C3. This holding recess C4 is fitted into the holding protrusion 201, so that the rotating engaging portion C4 engages with the rotating engaged portion 201. Here, the holding protrusion 201 of the second embodiment is provided on the base end side of the tip of the storage main body 20B. Therefore, the tip side of the tip of the holding protrusion 201 is formed as a flat surface. Also, in the engaging member C of the second embodiment, the distance between the urging receiving portion C2 and the urging engaging portion C3 is equal to or smaller than the distance from the tip of the holding protrusion 201 to the storage main body 20B. Therefore, when the engaging member C moves within the plunger accommodating portion 20 and the holding recess C4 is positioned further forward than the tip of the holding protrusion 201, the engagement between the rotation engaging portion C4 and the rotation engaged portion 201 is released.

[0106] The engaging member C of the second embodiment includes a rotation allowing mechanism T that allows relative rotation between the plunger accommodating portion 20 and the engaging member C around the central axis. Specifically, as shown in FIG. 22, the engaging member C of the second embodiment includes an engaging recess C6 as the rotation allowing mechanism T. This engaging recess C6 is provided so as to be recessed on the circumferential surface of the biasing receiving portion C2 and the biasing engaging portion C3. Also, the engaging recess C6 is formed larger in the width direction than the accommodating protrusion 203. Therefore, in the second embodiment, when the engaging member C is accommodated in the plunger accommodating portion 20, the engaging recess C6 fits (loosely fits) the accommodating protrusion 203. Therefore, the engaging recess C6 and the accommodating protrusion 203 move relatively around the central axis, and the plunger accommodating portion 20 and the engaging member C rotate relatively around the central axis. In the second embodiment, the engaging recess C6 moves around the central axis due to the circumferential biasing force of the plunger biasing portion A. Therefore, the engaging member C rotates around the central axis. The engaging recesses C6 in the second embodiment are provided between the first retaining recesses C40 and the second retaining recesses C41 on the circumferential surfaces of the urging receiving portion C2 and the urging engaging portion C3, which are circular when viewed from the central axis direction. Two engaging recesses C6 are provided in each of the urging receiving portion C2 and the urging engaging portion C3.

[0107] Moreover, the engaging member C of the second embodiment includes a rotation stopping mechanism U that stops the rotation of the plunger 12 and the engaging member C about the central axis. Specifically, as shown in FIG. 22, the engaging member C includes an engaging stop portion C60 as the rotation stopping mechanism U. The engaging stop portion C60 of the second embodiment is provided on the circumferential edge of the engaging recess C6 that is recessed in the peripheral surfaces of the biasing receiving portion C2 and the biasing engaging portion C3. Therefore, when the engaging recess C6 and the housing protrusion 203 move relatively around the central axis, the engaging stop portion C60 comes into contact with the housing protrusion 203, thereby stopping the rotation of the plunger housing portion 20 and the engaging member C about the central axis.

[0108] 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 function of the configuration different from that of the first embodiment will be described in detail. Therefore, the description will start from the step of removing the cap of the housing of the injection device 1 in the initial state, releasing the lock, and pushing the trigger part 23 into the plunger housing part 20.

[0109] In the second embodiment, when the trigger portion 23 is unlocked, the other guide portion a2 provided on the trigger body 232 is arranged so that its circumferential arrangement coincides with the one guide portion a1 provided on the cylindrical portion 230BA. The other guide portion a2 communicates with the one guide portion a1 in the central axis direction. Then, by pressing the trigger body 232, the other guide portion a2 overlaps with the other guide portion a2. Thus, the engagement between the trigger portion 23 and the engagement member C is released.

[0110] By releasing the engagement between the trigger portion 23 and the engagement member C, the urging of the plunger urging portion A, which was in a compressed state at the base end side of the plunger accommodating portion 20, is released. In the second embodiment, the trigger portion 23 moves from a urging force holding position, which holds the urging force of the plunger urging portion A so as not to be released, to a urging force releasing position, which releases the urging force of the plunger urging portion A. Then, the urging of the plunger urging portion A pushes the urging receiving portion C2, and the engagement member C and the syringe 10 move to the tip side of the plunger accommodating portion 20. Here, one end of the plunger urging portion A of the second embodiment is attached to the urging attachment portion 200c formed in the plunger accommodating portion 20. Also, the other end of the plunger urging portion A is attached to the urging attachment portion C7 provided on the engagement member C. Then, in a state in which the engagement member C is accommodated at the base end side of the plunger accommodating portion 20, the engagement holding mechanism Y1 is formed by the engagement between the holding recess C4 and the holding protrusion 201. Therefore, the engagement holding mechanism Y1 restricts the rotation of the engagement member C around the central axis relative to the plunger housing portion 20. In addition, the engagement holding mechanism Y1 of the second embodiment maintains the circumferential biasing force of the plunger biasing portion A by restricting the rotation of the engagement member C. Therefore, the plunger biasing portion A, the other end of which is attached to the engagement member C, does not rotate around the central axis when released from compression, but extends toward the tip side in the central axis direction, and pushes the engagement member C and the syringe 10 toward the tip side. Therefore, the engagement member C advances toward the tip side along the central axis direction until the engagement between the holding convex portion 201 and the holding concave portion C4 is released. In the second embodiment, the engagement concave portion C6 and the housing convex portion 203 are engaged with each other.

[0111] As the engaging member C advances toward the tip side of the plunger housing portion 20, the cover portion 111 moves in the central axis direction while compressing the barrel biasing portion B until the bottom surface abuts against the barrel receiving portion 210a. At this time, the holding recess 111b of the cover portion 111 moves along the holding protrusion of the barrel housing portion 21, similar to the first embodiment. Therefore, the barrel 11 moves toward the tip side in the central axis direction without rotating around the central axis. Thereafter, as shown in FIG. 23, the barrel 11 moves from the first position to the second position, and the injection needle 13 protrudes from the barrel housing portion 21.

[0112] As shown in FIG. 23, when the cover part 111 abuts against the barrel receiving part 210a, the movement of the barrel 11 toward the tip side stops. When the movement of the barrel 11 stops, the engagement member C and the plunger 12 are pushed by the force of the plunger biasing part A. Therefore, the engagement member C and the plunger 12 move toward the tip side in the central axis direction. Here, the plunger 12 of the second embodiment moves in the barrel 11 from the starting point to the end point (the tip of the barrel) while pushing the drug solution in the barrel 11 out of the barrel 11. At this time, the axial movement protrusion 120e provided on the rod 120 is aligned with the axial movement groove part 111c. Therefore, the plunger 12 moving in the barrel 11 does not rotate around the central axis. Specifically, as shown in FIG. 21, the axial movement protrusion 120e of the second embodiment is set to a length that does not come out of the axial movement groove part 111c of the cover part 111 when the plunger 12 reaches the tip of the barrel 11. Therefore, in the second embodiment, even if the plunger 12 reaches the tip of the barrel 11, the axial movement protrusion 120e does not come out of the axial movement groove 111c, and therefore the restriction by the rotation restriction part W is not released. Therefore, in the second embodiment, the plunger 12 that has moved in the central axis direction does not rotate around the central axis.

[0113] By the bias of the plunger biasing portion A, the engaging member C advances inside the accommodating body portion 20B while the holding recess C4 is aligned with the holding protrusion 201. In the second embodiment, as shown in Fig. 23, the plunger biasing portion A extends, and the engaging member C moves from the base end side to the tip end side of the plunger accommodating portion 20. In the second embodiment, as shown in Fig. 24, the engaging recess C6 is aligned with the accommodating protrusion 203.

[0114] When the engaging member C moves to the tip side of the plunger accommodating portion 20, the engagement between the holding convex portion 201 and the holding concave portion C4 is released. Specifically, as shown in Fig. 24, in the second embodiment, first, the engagement between the holding concave portion C4 provided in the biasing engaging portion C3 and the holding convex portion 201 of the plunger accommodating portion 20 is released. Thereafter, due to the biasing force of the plunger biasing portion A, the engaging member C moves along the central axis direction to the tip side of the plunger accommodating portion 20 while the holding concave portion C4 provided in the biasing receiving portion C2 moves along the holding convex portion 201.

[0115] The plunger biasing portion A biases the engaging member C in the state shown in FIG. 23, moving toward the tip side of the plunger accommodating portion 20 along the central axis line direction. Then, the engaging member C in the state shown in FIG. 25 is biased and fixed when the biased engaging portion C3 moves to a position adjacent to and facing the partition portion 22. At this time, as shown in FIG. 26, the engagement between the holding recess C4 formed in the bias receiving portion C2 and the holding protrusion 201 is released. Therefore, the restriction by the engaging holding mechanism Y1 that holds the engaging member C so as not to rotate with respect to the plunger accommodating portion 20 is released. In the second embodiment, the plunger 12 reaches the end point (the tip of the barrel 11) when the biased engaging portion C3 moves to a position adjacent to and facing the partition portion 22.

[0116] By releasing the restriction by the engagement holding mechanism Y1, the circumferential biasing force of the plunger biasing portion A is released. Here, as shown in FIG. 23 and FIG. 24, in the second embodiment, one end of the plunger biasing portion A is attached to the biasing attachment portion C7 of the engagement member C. In addition, in the second embodiment, the plunger accommodating portion 20 and the engagement member C are provided with a rotation allowing mechanism T. Specifically, the accommodating body portion 20B is provided with the accommodating protrusion 203, and the engagement member C is provided with the engagement recess C6. In the second embodiment, the engagement recess C6 and the accommodating protrusion 203 are fitted (loosely fitted). Therefore, in the second embodiment, the engagement recess C6 moves relatively around the central axis with respect to the accommodating protrusion 203 in accordance with the circumferential biasing force of the plunger biasing portion A. That is, in the second embodiment, the engagement member C rotates so as to change from the state of FIG. 26 to the state of FIG. 28 by utilizing the circumferential biasing force of the plunger biasing portion A configured as a torsion spring.

[0117] Thereafter, the rotation of the engaging member C around the central axis is stopped by the rotation stopping mechanism U. Specifically, in the second embodiment, as shown in FIG. 28, the engaging member C rotates around the central axis, causing the engagement stop portion C60 provided on the circumferential edge of the engaging recess C6 to abut against the accommodating protrusion 203. This stops the rotation of the engaging member C around the central axis. Note that in the second embodiment, as shown in FIG. 28, when the rotation of the plunger accommodating portion 20 and the engaging member C around the central axis is stopped, the holding protrusion 201 and the holding recess C4 are disposed at different positions in the circumferential direction. Therefore, the engaging member C is fixed so as not to move toward the base end side of the plunger accommodating portion 20.

[0118] The release hole C30 also rotates due to the rotation of the engaging member C. In the second embodiment, when the engagement stop portion C60 and the accommodation protrusion 203 come into contact with each other and the rotation of the engaging member C about the central axis line is stopped, the release hole C30 is disposed at a position that coincides with the first branch portion 120c and the pin portion 120b in the circumferential direction as shown in Figures 27 and 28. Therefore, the engagement between the biased engaging portion C3 and the biased engaged portion 120c is released, and the engagement between the plunger 12 and the engaging member C is released.

[0119] That is, the disengagement mechanism Z1 of the second embodiment disengages the plunger 12 from the engaging member C by rotating the engaging member C around the central axis relative to the plunger 12 using the circumferential biasing force of the plunger biasing portion A at the time when the engagement between the rotating engaged portion 201 and the rotating engaging portion C4 is released.

[0120] By releasing the engagement between the first branch portion 120c and the biasing engagement portion C3, the biasing force of the plunger biasing portion A on the syringe 10 is released. As a result, the barrel biasing portion B, which was compressed by the bias of the plunger biasing portion A, is released and pushes the syringe 10 toward the base end. As a result, the barrel 11 and the plunger 12 move toward the base end, and the pin portion 120b is fitted into the anti-rotation fitted portion C20. Therefore, the barrel 11 can be moved from the second position to the first position to accommodate the injection needle 13 in the housing.

[0121] As described above, in the injection device 1 of the second embodiment, the plunger biasing part A is configured to bias the engaging member C in a direction in which the engaging member C rotates around the central axis, and the disengagement mechanism Z1 is configured to rotate the engaging member C around the central axis relative to the plunger 12 by the circumferential biasing force of the plunger biasing part A, thereby disengaging the plunger 12 from the engaging member C. Therefore, by the engagement member C rotating around the central axis, the engagement between the plunger 12 and the engaging member C is released, and for example, the biasing force of the plunger biasing part A on the plunger 12 is released. Therefore, the syringe 10 is biased toward the other side in the central axis direction by the biasing force of the barrel biasing part B, and thereby the injection needle 13 can be retracted inside the housing.

[0122] In the second embodiment, the plunger biasing portion A is a torsion spring, and is configured to rotate the engaging member C by the circumferential biasing force of the torsion spring. Therefore, according to the configuration, the engagement between the plunger 12 and the engaging member C can be released by rotating the engaging member C by the circumferential biasing force of the plunger biasing portion A, which is a torsion spring.

[0123] In the second embodiment, the disengagement mechanism Z1 includes a rotational engagement portion C4 provided in the engagement member C and a rotational engaged portion 201 provided in the plunger accommodating portion 20, and is configured such that the rotational engagement portion C4 and the rotational engaged portion 201 are engaged with each other, the plunger 12 moves from the starting point toward the end point, and the engagement between the rotational engagement portion C4 and the rotational engaged portion 201 is released, so that the plunger 12 and the engagement member C rotate relatively around the central axis, and the engagement between the plunger 12 and the engagement member C is released. Therefore, a position for releasing the engagement between the rotational engagement portion C4 and the rotational engaged portion 201 can be set in accordance with the moving position of the plunger 12 relative to the barrel 11, so that, for example, the engagement between the rotational engagement portion C4 and the rotational engaged portion 201 can be released in accordance with the end point of the movement of the plunger 12.

[0124] In the second embodiment, the holding protrusion 201 and the holding recess C4 are fitted together, and the plunger 12 moves from the starting point toward the end point, and the fitting between the holding protrusion 201 and the holding recess C4 is released, whereby the engaging member C rotates relatively around the central axis, and the engagement between the plunger 12 and the engaging member C is released. Therefore, when the plunger 12 reaches the end point (the tip of the barrel 11), the engaging member C can rotate relatively to the plunger 12.

[0125] In addition, in the injection device 1 of the second embodiment, when the plunger 12 moves to the end point, the engagement between the holding recess C4 and the holding protrusion 201 is released, whereby the engaging member C rotates around the central axis and releases the engagement between the plunger 12 and the engaging member C. According to this configuration, for example, when the plunger 12 moves to the tip of the barrel 11 as the end point, the engagement between the holding recess C4 and the holding protrusion 201 is released, and when the injection of the medicinal liquid into the barrel 11 is completed, the syringe 10 is urged to the other side in the central axis direction by the urging of the barrel urging portion B, and the injection needle 13 can be retracted into the housing 2.

[0126] Moreover, the injection device 1 of the second embodiment includes a rotation stop mechanism U that stops the relative rotation between the plunger 12 and the engaging member C about the central axis. The rotation stop mechanism U includes an engagement stop portion C60 provided on the engaging member C and an engaged stopped portion 203 provided on the plunger accommodating portion 20, and the engagement stop portion C60 and the engaged stopped portion 203 engage with each other to stop the relative rotation between the plunger 12 and the engaging member C about the central axis. Therefore, by stopping the relative rotation between the plunger 12 and the engaging member C about the central axis, it is possible to prevent the plunger 12 and the engaging member C from continuing to rotate relative to each other about the central axis in the plunger accommodating portion 20.

[0127] In the injection device 1 of the second embodiment, the engaging member C rotates about the central axis, and when this rotation is stopped by the rotation stopping mechanism U, the holding convex portion 201 and the holding concave portion C4 are disposed at different positions in the circumferential direction. Therefore, in the second embodiment, the engaging member C after rotating about the central axis can be prevented from moving toward the base end side of the plunger biasing portion A.

[0128] In the second embodiment, a case has been described in which the rotation engaging portion is the holding recess C4, and the rotation engaged portion is the holding protrusion 201. However, this is not limiting, and for example, the rotation engaging portion may be the holding protrusion 201, and the rotation engaged portion may be the holding recess C4.

[0129] In the second embodiment, the engaging member C rotates around the central axis relative to the plunger 12. However, the present invention is not limited to this, and the plunger 12 may be rotated, or both the plunger 12 and the engaging member C may be rotated in the opposite directions.

[0130] In the first and second embodiments, the case where the tip projection 120h of the rod 120 is inserted into the connecting hole 121a of the piston 121 to connect the piston 121 and the rod 120 has been described. However, this is not limited to the above, and for example, as shown in FIG. 29, it is also possible to connect the piston 121 and the rod 120 by forming a male or female screw as the screw 121b on the piston and a female or male screw as the screw 120h on the rod and screwing them together. When the disengagement mechanism is configured to rotate the rod, the rotation direction of the rod can also be set to a direction in which the screwing is loosened. Then, the rotation of the rod when the plunger moves to just before the tip of the barrel 11 loosens the screwing, and the piston can be further pushed toward the end of the barrel 11 on the injection needle 13 side. This makes it possible to suppress the remaining liquid medicine in the barrel 11. Of course, the rotation direction of the rod 120 may be a direction in which the screwing is tightened. Also, the tip of the rod 120 may be configured to abut against an end face of the piston 121 to push the piston 121 into the barrel 11. In this case, the rod 120 may be configured not to have a tip protrusion 120h at its tip. The piston 121 may also be configured not to have a connecting hole 121a.

[0131] In the first and second embodiments, a case has been described in which the barrel 11 is biased by the barrel biasing portion B and abuts against the partition portion 22 when the injection needle 13 is retracted into the housing 2. However, the present invention is not limited to this, and the barrel 11 may be configured not to abut against the partition portion 22. Also, a configuration in which the partition portion 22 is not provided may be used.

[0132] In addition, the barrel biasing portion B and the plunger biasing portion A are not limited to springs, and may be made of rubber.

[0133] In the first embodiment, the biasing receiving portion C2 and the biasing engaging portion C3 of the engaging member C are provided separately, but the biasing engaging portion C3 can be the biasing receiving portion C2. In the first embodiment, the first branch portion 120c and the second branch portion 120d are formed in a cylindrical shape, but they may be in other shapes. For example, the first branch portion 120c may be a square column or a fan-shaped plate centered on the central axis O. In the case of a fan-shaped plate, it is preferable that the release hole C30 is also a fan-shaped hole. The second branch portion 120d may be an inclined surface corresponding to the inclined surface 111aa of the inclined portion 111a. In addition, the first branch portion 120c and the second branch portion 120d may be connected to each other in a rib shape extending in the direction of the central axis O.

[0134] In the first and second embodiments, the starting point is a position on the tip side of the base end of the barrel, and the end point is the tip of the barrel. However, this is not limited to the above, and the starting point can be the base end of the barrel (the base end of the main body 110b), or the end point can be on the base side of the tip of the barrel. In other words, as long as the starting point is on the base end side of the barrel and the end point is on the tip side, the starting point may be set at a position other than the base end of the barrel and the end point may be set at a position other than the tip of the barrel.

[0135] In addition, the relative rotation between the plunger and the engaging member is not limited to the first embodiment, and the plunger and the engaging member may rotate relative to each other from the beginning of the movement of the plunger. In other words, the engagement between the plunger and the engaging member may be released by rotating the plunger relative to each other about the central axis, and the position where the movement of the plunger from the starting point stops may be the end point.

[0136] In the first and second embodiments, the trigger portion is configured to release the bias of the plunger biasing portion by pressing the trigger portion. However, this is not limited to this. The predetermined operation for releasing the bias held by the plunger biasing portion may be, for example, an operation of pulling the trigger portion in the direction of the central axis or an operation of rotating the trigger portion around the central axis. In other words, it is sufficient that the trigger portion is configured to move between a biasing force holding position where the biasing force of the plunger biasing portion is not released and a biasing force releasing position where the biasing force of the plunger biasing portion is released from the biasing force holding position. [Explanation of symbols]

[0137] 1 ... injection device, 10 ... syringe, 11 ... barrel, 110 ... barrel body, 110a ... outer flange portion, 110b ... main body portion, 111 ... cover portion, 111a ... inclined portion (rotation engaged portion), 111aa ... inclined surface, 111ab ... horizontal surface, 111ac ... vertical surface, 111b ... holding recess, 111c ... axial movement groove portion, 111e ... insertion hole, 12 ... plunger, 120 ... rod, 120a ... rod body, 120b ... pin portion (rotation prevention fitting portion), 120c ... first branch portion (biased engaged portion), 120d ... second branch portion (rotation engagement portion), 120e ... axial movement protrusion, 12 0f...anti-slip portion, 120h...tip protrusion, 120h...screw, 121...piston, 121a...connecting hole, 121b...annular protrusion, 121b...screw, 13...injection needle, 2...housing, 20...plunger accommodating portion, 20a...axial cutout portion, 200...biasing base portion, 200a...tip side protrusion, 200b...insertion hole, 201...retaining protrusion, 201a...first retaining protrusion, 202...through hole, 21...barrel accommodating portion, 210...large barrel side barrel accommodating portion, 210a...barrel receiving portion, 210b...retaining protrusion, 211...small barrel side barrel accommodating portion, 211a...biasing base portion, 22... Partition portion, 220... through hole, 23... trigger portion, 230... trigger mounting portion, 230A... base end portion, 230B... cylindrical portion, 230BA... cylindrical body portion, 230BB... lock step portion, 230BC... convex portion, 230a... hook portion, 230bb... interlocking groove, 231... trigger lock operation portion, 231a... cylindrical main body portion, 231aa... rotation groove, 231b... inner flange portion, 231ba... interlocking convex portion, 232... trigger main body portion, 232a... top plate portion, 232b... outer skirt portion, 232ba... release groove, 232c... inner skirt portion, 232d... flat plate portion, A... with plunger biasing portion, B...barrel biasing portion, C...engagement member, C1...engagement body, C11...opening passage, C2...biased portion, C20...rotation prevention fitted portion, C3...biased engagement portion, C30...release hole, C4...retaining recess, C4...retaining protrusion, C40...first retaining recess, C41...second retaining recess, C5...trigger locking portion, C50...rib, K...cap, K1...needle cap retaining portion, K2...needle cap, O...center axis, V...locking mechanism portion, W...rotation restriction portion, X...rotation retention mechanism, Y...reverse rotation prevention means, Y1...engagement retention mechanism, Y2...reverse rotation prevention mechanism, Z1...disengagement mechanism

Claims

1. a syringe including a barrel having an injection needle at its tip, and a plunger inserted into the barrel so as to be capable of reciprocating between the base end side of the barrel and the injection needle side; a housing formed in a cylindrical shape for accommodating the syringe, the housing having a barrel accommodating section formed on one side in a central axial direction for accommodating the barrel so as to be movable 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 at a predetermined distance to one side from the accommodated state, and a plunger accommodating section formed on the other side of the barrel accommodating section for accommodating the plunger protruding from a base end side of the barrel; a barrel biasing portion provided in the barrel accommodating portion and biasing the barrel from one side of the housing to the other side; an engagement member disposed in the plunger accommodating portion and engaging with the plunger; a plunger biasing portion that engages with the engaging member and biases the plunger from the starting point toward the end point; a trigger portion configured to hold the plunger biasing portion so as not to release the bias of the plunger biasing portion when the barrel accommodates the injection needle by the barrel biasing portion and the plunger has a tip located at the starting point against the bias of the plunger biasing portion, and to release the hold by performing a predetermined operation; a disengagement mechanism that disengages the plunger from the starting point toward the end point by the biasing force of the plunger biasing portion, and disengages the plunger from the engaging member and the engaging member by rotating the plunger relative to the engaging member about a central axis, thereby positioning the plunger at the end point; The disengagement mechanism includes a rotational engaging portion provided on the plunger and a rotational engaged portion provided on the barrel, An injection device characterized in that the plunger moves from the starting point to the end point and the rotational engagement portion engages with the rotational engaged portion, causing the plunger to rotate around a central axis and releasing the engagement between the plunger and the engaging member.

2. 2. The injection device of claim 1, wherein when the plunger moves from the starting point to just before reaching the end point, the rotational engagement portion engages with the rotationally engaged portion, causing the plunger to rotate around a central axis and disengaging the plunger from the engagement member.

3. A syringe comprising: a barrel having an injection needle at its tip; and a plunger inserted into the barrel so as to be capable of reciprocating between the base end of the barrel and the injection needle; a housing formed in a cylindrical shape for accommodating the syringe, the housing having a barrel accommodating section formed on one side in a central axial direction for accommodating the barrel so as to be movable 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 at a predetermined distance to one side from the accommodated state, and a plunger accommodating section formed on the other side of the barrel accommodating section for accommodating the plunger protruding from a base end side of the barrel; a barrel biasing portion provided in the barrel accommodating portion and biasing the barrel from one side of the housing to the other side; an engagement member disposed in the plunger accommodating portion and engaging with the plunger; a plunger biasing portion that engages with the engaging member and biases the plunger from the starting point toward the end point; a trigger portion configured to hold the plunger biasing portion so as not to release the bias of the plunger biasing portion when the barrel accommodates the injection needle by the barrel biasing portion and the plunger has a tip located at the starting point against the bias of the plunger biasing portion, and to release the hold by performing a predetermined operation; a disengagement mechanism that disengages the plunger from the starting point toward the end point by the biasing force of the plunger biasing portion, and disengages the plunger from the engaging member and the engaging member by rotating the plunger relative to the engaging member about a central axis, thereby positioning the plunger at the end point; The plunger biasing portion is configured to bias the engaging member in a direction in which the engaging member rotates about a central axis line, The injection device is characterized in that the disengagement mechanism is configured to disengage the plunger and the engagement member by rotating the engagement member about a central axis relative to the plunger using the biasing force of the plunger biasing portion.

4. 4. The injection device according to claim 3, wherein the plunger biasing portion is a torsion spring, and the engaging member is rotated by a biasing force generated by torsion of the torsion spring.

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