Patent Description:
An injector for injecting a fluid is conventionally known. For example, the injector described in Patent Document <NUM> is configured such that after pushing out a necessary amount of fluid through a discharge port to the outside of a barrel, the fluid remaining inside the barrel does not leak automatically through the discharge port, i.e., "subsequent dripping" of the fluid does not occur.

Specifically, in the case of the injector described in Patent Document <NUM>, a disk-shaped seal body is integrally disposed at a front end of a plunger. An outer circumferential end of the seal body is in close contact with an inner circumferential surface of the barrel.

When the plunger advances toward the discharge port of the barrel, the disk-shaped seal body pushes and moves the fluid toward the discharge port while elastically deforms into a closed umbrella shape. When the plunger stops, the seal body returns from the closed umbrella shape to the disk shape. In this case, a central portion of the seal body is shifted in a direction away from the discharge port without changing a position of the inner circumferential surface of the barrel at which the outer circumferential end of the seal body is in contact. As a result, the fluid is drawn toward the seal body, and the subsequent dripping of the fluid is suppressed.

Patent Document <NUM> discloses a plastic injection molded plunger for a medical syringe and a medical syringe having such plunger, wherein the plunger comprises one or more sealing, and, in cross-section, a sealing lip is furthermore angled toward the front or the rear in an advancement direction for the discharge of liquid from the syringe during use. A channel is formed with respect to a central region of the plunger, which channel, viewed in cross-section, projects radially beyond the largest plunger diameter.

Patent Document <NUM> discloses a stopper adapted for attachment with a plunger rod for use within a syringe barrel including a main body portion defining an open rearward end configured to receive the plunger rod.

Patent Document <NUM> discloses a plunger for use in a syringe and a syringe comprising such a plunger. The plunger includes a pressure member extending around the circumference of a generally cylindrical body of the plunger. The pressure member is in substantially sealing contact with the plunger body. The pressure member forms a substantially sealing engagement with the inner wall of the syringe. Further, the pressure member comprises a flange attached at a rearward portion of the flange to a body of the plunger. The flange extends forward and radially outward to form a circumferential channel between the flange and the body of the plunger.

To prevent the seal body closely contact with the inner circumferential surface of the barrel from coming off to the outside of the barrel, an injector having the seal body and the plunger coming into separable contact with each other is required. This allows the seal body to remain in the barrel without retracting even if the plunger is retracted. As a result, air is prevented from entering the fluid in the barrel from the base end side of the barrel. This also prevents air from entering from the discharge port due to retracting of the seal body.

Therefore, a problem to be solved by the present invention is to bring a seal body and a plunger into separable contact with each other in an injector capable of suppressing subsequent dripping of a fluid.

To solve the problem described above, the present invention provides an injector as defined in appended claim <NUM>.

According to the present invention, the seal body and the plunger can be brought into separable contact with each other in the injector capable of suppressing subsequent dripping of a fluid.

An injector according to the present invention comprises a cylindrical barrel, a movable body housed in the barrel, and a plunger coming into separable contact with the movable body; the movable body includes a main body having an outer diameter smaller than an inner diameter of the barrel, a disk-shaped seal body attached to a front end of the main body and including an outer circumferential end brought into close contact with an inner circumferential surface of the barrel, and at least one projecting portion projecting from the main body toward the inner circumferential surface of the barrel; and a distance from a central axis of the movable body to a leading end of the at least one projecting portion is smaller than a half of an outer diameter of the seal body. Further, the movable body and the plunger are configured to separate from each other by retracting the plunger.

The at least one projecting portion may be a flange. In this case, an outer diameter of the flange is made smaller than the outer diameter of the seal body.

The outer diameter of the flange may be smaller than the inner diameter of the barrel. As a result, the flange can be moved without strong contact with the inner circumferential surface of the barrel, i.e., in a state of substantially zero friction force.

A distance between the seal body and the flange may be larger than the outer diameter of the seal body. As a result, the movable body is restrained from tilting.

The plunger may include a planar-shaped contact surface at a front end thereof, and the movable body may include a planar-shaped rear end surface coming into contact with the contact surface of the plunger. As a result, the movable body can be pushed and moved by the plunger without tilting.

The plunger may include a guide pin projecting from the contact surface, and the movable body may include in the rear end surface a guide hole receiving the guide pin in a manner enabling forward and backward movement. Since the guide pin is guided by the guide hole, the rear end surface of the movable body and the contact surface of the plunger can appropriately contact with each other.

<FIG> is an external view of an injector according to a first embodiment of the present invention, and <FIG> is a partial cross-sectional view of the injector.

As shown in <FIG> and <FIG>, an injector <NUM> includes a barrel <NUM> containing, for example, a pasty fluid, a movable body <NUM> movably housed in the barrel <NUM>, and a plunger <NUM> for pushing and moving the movable body <NUM>. The injector <NUM> also has a nozzle tip <NUM> attached to a leading end 12a of the barrel <NUM> and a finger grip <NUM> rotatably fitted to a base end 12b of the barrel <NUM>.

<FIG> is a cross-sectional view of the barrel, and <FIG> is an enlarged cross-sectional view of the barrel shown in <FIG>.

As shown in <FIG>, the barrel <NUM> is a cylindrical member having a central axis C1, and is made of a resin material, for example. The barrel <NUM> includes a discharge port 12c at the leading end 12a and a flange portion 12d at the base end 12b. By attaching the nozzle tip <NUM> to the leading end 12a of the barrel <NUM>, the discharge port 12c is connected to a nozzle inside flow passage communicating with the outside in the nozzle tip <NUM>. The flange portion 12d functions as a stopper preventing the finger grip <NUM> rotatably fitted to a base end side portion of the barrel <NUM> from falling off.

As shown in <FIG>, a circumferential groove 12f is formed in a base end side portion of an inner circumferential surface 12e of the barrel <NUM>. The reason why the circumferential groove 12f is formed will be described later.

<FIG> is a perspective view of the movable body, and <FIG> is a partial cross-sectional view of the movable body.

As shown in <FIG>, the movable body <NUM> is a substantially cylindrical member having a central axis C2. The movable body <NUM> is made of an elastically deformable resin material, for example. Specifically, the movable body <NUM> is made of a material easily elastically deformed as compared to the barrel <NUM>.

The movable body <NUM> includes a main body 14a, a seal body 14b disposed on the main body 14a, and a flange 14c disposed on the main body 14a.

The main body 14a of the movable body <NUM> is cylindrical and has an outer diameter d2 smaller than an inner diameter d1 of the barrel <NUM> shown in <FIG>. Therefore, while the movable body <NUM> is housed in the barrel <NUM>, a clearance is generated between the main body 14a and the inner circumferential surface 12e of the barrel <NUM>.

The seal body 14b of the movable body <NUM> has a disk shape and has an outer circumferential end brought into close contact with the inner circumferential surface 12e of the barrel <NUM> in a slidable and fluid-tight manner. Although the seal body 14b and the main body 14a are integrated as one part, the seal body 14b and the main body 14a may be separate parts.

For close contact of the outer circumferential end with the inner circumferential surface 12e of the barrel <NUM> in a fluid-tight manner, the seal body 14b has an outer diameter d3 larger than the inner diameter d1 of the barrel <NUM>. The outer diameter d3 of the seal body 14b is larger than the outer diameter d2 of the main body 14a of the movable body <NUM>.

Additionally, the seal body 14b has a central portion attached to a front end of the main body 14a (the end closer to the leading end 12a of the barrel <NUM>). Additionally, an outer circumferential side portion of the seal body 14b is away from the main body 14a when the portion is in a free state (when the movable body <NUM> is present outside the barrel <NUM>).

The flange 14c of the movable body <NUM> is a projecting portion projecting from the main body toward the inner circumferential surface of the barrel <NUM> and is disposed at a rear end of the main body 14a (the end closer to the base end 12b of the barrel <NUM>). The flange 14c has an outer diameter d4 smaller than the outer +diameter d3 of the seal body 14b. In the case of the first embodiment, the outer diameter d4 of the flange 14c is smaller than the inner diameter d1 of the barrel <NUM> and larger than the outer diameter d2 of the main body 14a. The reason why the flange 14c as described above is disposed on the movable body <NUM> will be described later.

For separable contact with the plunger <NUM>, the movable body <NUM> also includes a planar-shaped rear end surface 14d orthogonal to the central axis C2 and includes a non-penetrating hole-shaped guide hole 14e in the rear end surface 14d.

<FIG> is an external view of the plunger.

As shown in <FIG>, the plunger <NUM> is a member for pushing and moving the movable body <NUM> housed in the barrel <NUM> toward the leading end 12a (i.e., the discharge port 12c) of the barrel <NUM>, has a central axis C3, and is made of a resin material, for example. The plunger <NUM> is configured to come into separable contact with the movable body <NUM>.

Specifically, the plunger <NUM> includes a contact portion 16a coming into contact with the movable body <NUM> on the front end side (the side closer to the leading end 12a of the barrel <NUM>). The contact portion 16a has an outer diameter d5 smaller than the inner diameter d1 of the barrel <NUM>. The contact portion 16a includes a planar-shaped contact surface 16b coming into surface contact with the planar-shaped rear end surface 14d of the movable body <NUM>.

The plunger <NUM> includes a guide pin 16c projecting from the contact surface 16b of the contact portion 16a. While the rear end surface 14d of the movable body <NUM> is in surface contact with the contact surface 16b of the plunger <NUM>, the guide pin 16c is received in the guide hole 14e of the movable body <NUM>. An outer diameter d6 of the guide pin 16c is smaller than an inner diameter d7 of the guide hole 14e shown in <FIG> so that the guide pin is received in the guide hole 14e of the movable body <NUM> in a manner enabling forward and backward movement. Since the guide pin 16c is guided by the guide hole 14e, the contact surface 16b of the plunger <NUM> can appropriately come into surface contact with the rear end surface 14d of the movable body <NUM>. Specifically, the movable body <NUM> and the plunger <NUM> can come into contact with each other in a state in which the central axis C2 of the movable body <NUM> and the central axis C3 of the plunger <NUM> are arranged substantially on the same straight line. As a result, the plunger <NUM> can push and move the movable body <NUM> toward the leading end 12a of the barrel <NUM> without tilting.

According to the plunger <NUM> as described above, the movable body <NUM> can be pushed and moved toward the leading end 12a of the barrel <NUM> by advancing the plunger <NUM>. Additionally, the movable body <NUM> and the plunger <NUM> can be separated from each other by simply retracting the plunger <NUM>.

Since the plunger <NUM> is not fixed to the movable body <NUM> while the seal body 14b is in close contact with the inner circumferential surface 12e of the barrel <NUM>, the plunger <NUM> possibly comes off from the barrel <NUM>. For example, if the injector <NUM> is in a state with the nozzle tip <NUM> located downward and a user grasps only the plunger <NUM> to lift the injector <NUM>, the barrel <NUM> may fall off from the plunger <NUM> due to its own weight.

To prevent the plunger <NUM> from coming off from the barrel <NUM> in this way, stoppers 16d are disposed on the plunger <NUM> as shown in <FIG>.

In the case of the first embodiment, the two stoppers 16d are disposed oppositely to each other across the central axis C3 of the plunger <NUM>. Each of the two stoppers 16d is an elastically-deformable plate spring-shaped member including a fixed end 16e attached to the plunger <NUM> and a free end 16f displaceable in a radial direction of the barrel <NUM> (a direction orthogonal to the central axis C1 of the barrel <NUM>). In the case of the first embodiment, the stoppers 16d and the plunger <NUM> are integrated as one part.

In the case of the first embodiment, the free end 16f of the stopper 16d is located on the base end 12b side of the barrel <NUM> with respect to the fixed end 16e. The free end 16f is farther than the fixed end 16e from the central axis C3 of the plunger <NUM>. Therefore, the stopper 16d extends from the leading end 12a side to the base end 12b side of the barrel <NUM> and toward the inner circumferential surface 12e of the barrel <NUM>.

As shown in <FIG>, a distance L1 between the free ends 16f of the two stoppers 16d is larger than the inner diameter d1 of the barrel <NUM> when the free ends are in a free state (when the plunger <NUM> is present outside the barrel <NUM>). Therefore, when the stoppers 16d of the plunger <NUM> are located inside the barrel <NUM>, each of the two stoppers 16d is elastically deformed by the inner circumferential surface 12e of the barrel <NUM> such that the free ends 16f come closer to each other. This brings the free ends 16f of the stopper 16d into elastic contact with the inner circumferential surface 12e of the barrel <NUM> in the radial direction of the barrel <NUM>. As a result, a friction force is generated between the barrel <NUM> and the free ends 16f of the stopper 16d, and the plunger <NUM> is restrained from coming off from the barrel <NUM>. The term "elastic contact" as used herein means that a portion of an object during elastic deformation is in contact with another object in a restoring direction in which the object is restored to an original shape.

An elastic force of the stoppers 16d, i.e., the friction force between the inner circumferential surface 12e of the barrel <NUM> and the free ends 16f of the stoppers 16d, is at a level preventing the barrel <NUM> from coming off when a user grasps only the plunger <NUM> of the injector <NUM> in a posture with the nozzle tip <NUM> located downward, or at a level preventing the plunger <NUM> from coming off when a user grasps only the barrel <NUM> of the injector <NUM> in a posture with the nozzle tip <NUM> located upward. Additionally, this elastic force (i.e., friction force) is at a level allowing the user to push and move the plunger <NUM> toward the leading end 12a of the barrel <NUM>. To achieve such an elastic force (i.e., friction force), the materials of the barrel <NUM> and the stoppers 16d, the shape of the stoppers 16d, etc. are appropriately selected.

According to the stoppers 16d as described above, the plunger <NUM> can be prevented from coming off from the barrel <NUM> without disposing a convex portion on the inner circumferential surface 12e of the barrel <NUM>. Therefore, when the movable body <NUM> is housed into the barrel <NUM>, the seal body 14b is not damaged by the convex portion disposed on the inner circumferential surface 12e.

According to the stoppers 16d as described above, the plunger <NUM> can be anchored at an arbitrary position on the inner circumferential surface 12e of the barrel <NUM>. As a result, the injector <NUM> can have high usability.

Furthermore, in the case of the first embodiment, the two stoppers 16d are arranged oppositely to each other across the central axis C3 of the plunger <NUM>, so that the central axis C3 of the plunger <NUM> can be aligned with the central axis C1 of the barrel <NUM>.

Although the free ends 16f of the stoppers 16d are in elastic contact with the inner circumferential surface 12e of the barrel <NUM>, if the user moves the plunger <NUM> backward, the free end 16f slides on the inner circumferential surface 12e, and the plunger <NUM> finally comes off from the barrel <NUM>. To deal with such coming-off due to the user, as shown in <FIG>, the circumferential groove 12f is formed in a portion near the base end 12b in the inner circumferential surface 12e of the barrel <NUM>. The free ends 16f of the stoppers 16d engage with (fall and fit into) the circumferential groove 12f, so that the plunger <NUM> is restricted from moving toward the base end side of the barrel <NUM>, and as a result, the plunger <NUM> is prevented from coming off from the barrel <NUM>.

When the plunger <NUM> is housed into the barrel <NUM>, the free ends 16f of the stoppers 16d may be caught in the circumferential groove 12f, which possibly makes it unable to smoothly move the plunger <NUM> toward the leading end 12a of the barrel <NUM>. As a countermeasure, as shown in <FIG>, the circumferential groove 12f includes a slope surface <NUM> extending from a bottom potion thereof toward the leading end 12a of the barrel <NUM> and sloping with respect to the inner circumferential surface 12e. Due to the slope surface <NUM>, the free end 16f falling into the circumferential groove 12f can return onto the inner circumferential surface 12e. As a result, the free ends 16f of the stoppers 16d can pass through the circumferential groove 12f without being caught.

When the movable body <NUM> is housed into the barrel <NUM>, the slope surface <NUM> can also prevent the seal body 14b of the movable body <NUM> from being caught in the circumferential groove 12f. As a result, the seal body 14b can be prevented from being damaged by the circumferential groove 12f.

While describing the operation of the injector <NUM> according to the first embodiment, other features of the injector <NUM> will hereinafter be described with reference to <FIG>.

<FIG> is an enlarged cross-sectional view of the barrel while the plunger and the movable body are stopped.

As shown in <FIG>, the seal body 14b of the movable body <NUM> is in close fluid-tight contact with the inner circumferential surface 12e of the barrel <NUM>, so that a fluid F is contained in the barrel <NUM> without leaking from the base end side of the barrel <NUM> to the outside.

<FIG> is an enlarged cross-sectional view of the barrel during movement of the plunger and the movable body toward the leading end of the barrel.

As shown in <FIG>, while the rear end surface 14d of the movable body <NUM> and the contact surface 16b of the plunger <NUM> are in contact with each other, the movable body <NUM> is pushed and moved toward the leading end 12a of the barrel <NUM> by the plunger <NUM>. During movement of the movable body <NUM>, the seal body 14b is elastically deformed. Specifically, due to the friction force generated between the outer circumferential end of the seal body 14b and the inner circumferential surface 12e of the barrel <NUM>, the seal body 14b is elastically deformed such that the outer circumferential side portion of the seal body 14b approaches the main body 14a. The seal body 14b moves in this elastically deformed state and pushes and moves the fluid F toward the discharge port 12c.

<FIG> is an enlarged cross-sectional view of the barrel during movement of the plunger in a direction away from the movable body.

As shown in <FIG>, when the plunger <NUM> moves in a direction away from the movable body <NUM>, i.e., toward the base end of the barrel <NUM>, the movable body <NUM> is separated from the plunger <NUM> and stops in the barrel <NUM> in this state.

Immediately after the movable body <NUM> stops, as shown in <FIG>, the seal body 14b is returned (restored) to the original shape with the outer circumferential side portion separated from the main body 14a. In this case, the movable body <NUM> entirely retracts toward the base end of the barrel <NUM> without changing the contact position on the inner circumferential surface 12e of the barrel <NUM> in contact with the outer circumferential end of the seal body 14b. As a result, the fluid F in the nozzle tip <NUM> is drawn toward the seal body 14b, and the subsequent dripping of the fluid F is suppressed.

To allow the movable body <NUM> to retract toward the base end of the barrel <NUM> through the restoration of the seal body 14b without changing the position of contact of the seal body 14b with the barrel <NUM>, the plunger <NUM> needs to retreat at the same time. In other words, a restoring force of the seal body 14b needs to exceed the friction force between the free ends 16f of the stoppers 16d of the plunger <NUM> and the inner circumferential surface 12e of the barrel <NUM>. For this purpose, the material of the seal body 14b, the shape of the seal body 14b, etc. are appropriately selected.

When the movable body <NUM> retracts through the restoration of the seal body 14b without changing the position of contact of the seal body 14b with the barrel <NUM> as described above, the flange 14c is moved along the inner circumferential surface 12e of the barrel <NUM>. As a result, the movable body <NUM> can retreat in the extending direction of the central axis C1 of the barrel <NUM>. If the flange 14c does not exit, the movable body <NUM> retracts in a direction tilted with respect to the central axis C1 of the barrel <NUM>, so that the movable body <NUM> may have a posture in which a portion of an outer edge of the rear end surface 14d comes into contact with the inner circumferential surface 12e of the barrel <NUM>, i.e., a tilted posture. If the movable body <NUM> is tilted, the adhesion between the seal body 14b and the inner circumferential surface 12e of the barrel <NUM> is partially weakened, so that the fluid F may leak to the base end side of the barrel <NUM>.

In the case of the first embodiment, the outer diameter d4 of the flange 14c of the movable body <NUM> is smaller than the inner diameter d1 of the barrel <NUM>. Therefore, the flange 14c can be moved without strong contact with the inner circumferential surface 12e of the barrel <NUM>, i.e., in a state of substantially zero friction force. Alternatively, the outer diameter d4 of the flange 14c of the movable body <NUM> may be equal to or larger than the inner diameter d1 of the barrel <NUM>. However, the friction force between the flange 14c and the barrel <NUM> must be smaller than the friction force between the seal body 14b and the barrel <NUM>. Otherwise, the restoration of the seal body 14b and the retraction of the movable body <NUM> due to the restoration cannot be achieved.

In the case of the first embodiment, as shown in <FIG>, the distance L2 between the seal body 14b and the flange 14c in the movable body <NUM> is made larger than the outer diameter d3 of the seal body 14b. Therefore, when the movable body <NUM> retracts due to the restoration of the seal body 14b, the movable body <NUM> is hardly tilted (as compared to when the distance L2 is smaller than the outer diameter d3).

As shown in <FIG>, the plunger <NUM> separated from the movable body <NUM> is kept housed in the barrel <NUM> by the stoppers 16d without coming off from the barrel <NUM>.

<FIG> is a partially enlarged cross-sectional view of the barrel while the plunger is restricted from coming off from the barrel by the circumferential groove.

As shown in <FIG>, the plunger <NUM> during retraction toward the base end of the barrel <NUM> due to pulling by the user is restrained by engagement of the free ends 16f of the stoppers 16d with the circumferential groove 12f. As a result, the plunger <NUM> is prevented from coming off from the barrel <NUM>.

According to the first embodiment as described above, the seal body and the plunger can be brought into separable contact with each other in the injector capable of suppressing the subsequent dripping of the fluid.

A second embodiment is substantially the same as the first embodiment as descried above except that the form of the stoppers disposed on the plunger is different. Therefore, the second embodiment will be described mainly in terms of different points. The same reference numerals are given to constituent elements in the second embodiment that are substantially the same as the constituent elements in the first embodiment described above.

<FIG> is an enlarged cross-sectional view of a leading end side portion of a barrel in an injector according to the second embodiment. <FIG> is an enlarged cross-sectional view of a base end side portion of the barrel.

As shown in <FIG>, in an injector <NUM> according to the second embodiment, a plunger <NUM> includes stoppers 116d. Each of the stoppers 116d is a plate spring-shaped member including a fixed end 116e attached to the plunger <NUM> and a free end 116f elastically contacting the inner circumferential surface 12e of the barrel <NUM>.

In the case of the second embodiment, unlike the stopper 16d of the first embodiment, the free end 116f of the stopper 116d is located on the leading end side of the barrel <NUM> with respect to the fixed end 116e. Therefore, a contact surface 116b of the plunger <NUM> coming into contact with the rear end surface 14d of the movable body <NUM> is closer to the free end 116f of the stopper 116d as compared to the first embodiment shown in <FIG>.

Thus, as shown in <FIG>, when the free end 116f of the stopper 116d is engaged with the circumferential groove of the barrel <NUM>, the contact surface 116b of the plunger <NUM> is located closer to the base end 12b of the barrel <NUM>. In other words, the movable body <NUM> having the rear end surface 14d brought into contact with the contact surface 116b is also disposed closer to the base end 12b of the barrel <NUM>. As a result, a larger amount of the fluid can be contained in the barrel <NUM>.

In the second embodiment as described above, as with the first embodiment, the seal body and the plunger can be brought into separable contact with each other in the injector capable of suppressing the subsequent dripping of the fluid.

In the case of the first embodiment described above, the stoppers preventing the plunger from coming off from the barrel are disposed on the plunger. In contrast, in the case of a third embodiment, stoppers are disposed on the barrel. Therefore, the third embodiment will be described mainly in terms of the different stoppers. The same reference numerals are given to constituent elements in the third embodiment that are substantially the same as the constituent elements in the first embodiment described above.

<FIG> is a partial cross-sectional view of an injector according to the third embodiment. <FIG> is a cross-sectional view of the injector taken along a line A-A shown in <FIG>. <FIG> is an enlarged cross-sectional view of a barrel, showing stoppers when the movable body is housed into the barrel. In <FIG>, the nozzle tip and the finger grip are not shown.

As shown in <FIG> and <FIG>, in an injector <NUM> according to the third embodiment, no stopper is disposed on a plunger <NUM>. Instead, as shown in <FIG>, a pair of stoppers 212f facing each other is disposed on a barrel <NUM>.

Specifically, in the case of the third embodiment, the stoppers 212f are made up of portions of the barrel <NUM> each interposed between two slits <NUM> formed to extend from a base end 212b of the barrel <NUM>. As a result, a portion of the barrel <NUM> interposed between base portions of the two slits <NUM> is defined as a fixed end <NUM> of the stopper 212f. A claw 212j brought into elastic contact with the plunger <NUM> is disposed on the inner side of a free end 212i of each of the paired stoppers 212f. Therefore, the stopper 212f is a plate spring-shaped member (a plate spring-shaped member integrated with the barrel <NUM>) having the fixed end <NUM> attached to the barrel <NUM> and the free end 212i brought into elastic contact with the plunger <NUM> (via the claws 212j).

A distance between the claws 212j of the pair of the stoppers 212f is made smaller than an outer diameter of a shaft portion 216b of the plunger <NUM>. As a result, the pair of the claws 212j holds the shaft portion 216b of the plunger <NUM>. Consequently, the plunger <NUM> is prevented from coming off from the barrel <NUM>.

The plunger <NUM> during retraction toward the base end 212b of the barrel <NUM> due to pulling by the user is restrained when a contact portion 216a for contact with the movable body <NUM> is brought into contact with the claws 212j. As a result, the plunger <NUM> is prevented from coming off from the barrel <NUM>.

As shown in <FIG>, when the movable body <NUM> is housed into the barrel <NUM>, the pair of the stoppers 212f is elastically deformed such that the free ends 212i move away from each other. As a result, the movable body <NUM> can be housed into the barrel <NUM> without bringing the claws 212j of the stoppers 212f into contact with the seal body 14b.

In the third embodiment as described above, as with the first embodiment, the seal body and the plunger can be brought into separable contact with each other in the injector capable of suppressing the subsequent dripping of the fluid.

Although the present invention has been described with three embodiments, the present invention is not limited to these embodiments.

For example, in the case of the first embodiment, as shown in <FIG>, the planar-shaped rear end surface 14d of the movable body <NUM> and the planar-shaped contact surface 16b of the plunger <NUM> come into separable contact with each other. Therefore, the movable body <NUM> and the plunger <NUM> are configured to come into plane contact with each other. However, the embodiments of the present invention are not limited thereto. For example, the movable body may include a hemispherical concave portion at the rear end thereof, and the plunger may include a hemispherical convex portion engageable with the concave portion.

In the case of the first embodiment described above, as shown in <FIG>, the movable body <NUM> has the flange 14c disposed at the rear end of the main body 14a. The flange may be disposed in a portion of the main body other than the rear end. However, to suppress the tilt of the movable body, the seal body is preferably separated from the flange.

Regarding the flange, at least three projecting portions disposed at regular intervals on the movable body in a circumferential direction of the main body can function as a substitute for the flange. In this case, a distance from the central axis of the movable body to a leading end of at least one of the projecting portions is made smaller than a half of the outer diameter of the seal body.

Claim 1:
An injector (<NUM>, <NUM>, <NUM>) comprising:
a cylindrical barrel (<NUM>, <NUM>);
a movable body (<NUM>) housed in the barrel (<NUM>, <NUM>); and
a plunger (<NUM>, <NUM>, <NUM>) coming into separable contact with the movable body (<NUM>),
wherein the movable body (<NUM>) includes
a main body (14a) having an outer diameter smaller than an inner diameter of the barrel (<NUM>, <NUM>),
a disk-shaped seal body (14b) attached to a front end of the main body (14a) and including an outer circumferential end brought into close contact with an inner circumferential surface (12e) of the barrel (<NUM>, <NUM>), and
at least one projecting portion (14c) projecting from the main body (14a) toward the inner circumferential surface (12e) of the barrel (<NUM>, <NUM>),
wherein a distance from a central axis of the movable body (<NUM>) to a leading end of the at least one projecting portion (14c) is smaller than a half of an outer diameter of the seal body (14b), and
wherein the movable body (<NUM>) and the plunger (<NUM>, <NUM>, <NUM>) are configured to separate from each other by retracting the plunger (<NUM>, <NUM>, <NUM>),
characterized in that a pair of stoppers (16d, 116d, 212f) are disposed on one of the barrel (<NUM>, <NUM>) and the plunger (<NUM>, <NUM>, <NUM>), and the stoppers (16d, 116d, 212f) come into elastic contact with the other one of the barrel (<NUM>, <NUM>) and the plunger (<NUM>, <NUM>, <NUM>) in a radial direction of the barrel (<NUM>, <NUM>).