SYRINGE

In a syringe that allows an administration operation while a coil spring is held by a spring holder in a compressed state and a further thrust operation of the syringe barrel after completion of administration releases the coil spring from the hold of the spring holder, the coil spring is prevented from being released from the hold of by the spring holder inadvertently during administration. When, upon completion of administration of the liquid drug, the syringe barrel 2 is thrust toward the distal end relative to the cover 6, the spring holder 17 is configured to be movable from a hooked position toward the distal end relative to the cover 6, where the hook members 17b are hooked on the cover 6 when in the hooked position, and a guide surface S is provided on the inner periphery of the cover 6 adapted, when the spring holder 17 has moved from the hooked position toward the distal end, to cause the hook members 17b to radially deform such that the hook members cease to be hooked on the cover 6.

TECHNICAL FIELD

The present invention relates to a syringe.

BACKGROUND ART

To prevent a patient, when injecting a biomedical anticancer drug, an antirheumatic drug or other drugs at home, from accidentally hurting himself/herself with the needle, the applicant of the present application has been developing disposable syringes whose needle can be placed within the body until injection and, after injection, can be retracted back into the body, and has disclosed results of this effort in Patent Documents 1 and 2 listed below.

PRIOR ART DOCUMENTS

Patent Documents

Patent Document 1: JP 2014-212832 A

Patent Document 2: JP 2016-202438 A

In each of the syringes disclosed in Patent Documents 1 and 2, the injection needle is placed within a cover and a plunger during storage before use. During storage, the cover and plunger are arranged in the axial direction to abut each other to prevent the plunger from being thrust in relative to the cover. During use, the cover and plunger are rotated relative to each other to reduce the total axial length of the cover and plunger such that the tip of the injection needle protrudes outward from the distal-end portion of the cover and, thereafter, the syringe barrel is thrust in relative to the cover and plunger to achieve administration of the liquid drug.

Further, the cover is composed of a first cover member (i.e., cylindrical body) and a second cover member (i.e., safety cover) that can be axially moved relative to each other by a small amount, where, upon completion of administration, the syringe barrel can be thrust yet more strongly to increase the total axial length of the first and second cover members. When the total length of the first and second cover members has been increased to some extent, the hook members of the spring holder are broken to release the coil spring, and the resulting biasing force of the coil spring causes the cover to axially move relative to the injection needle further in the direction of the distal end such that the injection needle is retracted back into the cover.

SUMMARY OF THE INVENTION

Problems to be Solved by the Invention

A problem with the above-described conventional syringe construction is that, during administration, if the syringe barrel is momentarily thrust strongly, this strong thrust force is transmitted up to the hook members of the spring holder, potentially breaking the hook members even though administration is not yet completed.

Means for Solving the Problems

In connection with a syringe including:

a syringe barrel having an open distal-end portion and defining an interior space to be filled with a liquid drug;

a gasket fitted into the syringe barrel to seal in the liquid drug;

an injection needle having a base-end portion adapted to pierce through the gasket at least during administration of the liquid drug;

a plunger attached to the gasket and holding the injection needle;

a cover capable of being axially moved relative to the injection needle between a storage position and an administration position, wherein the cover contains therewithin a distal-end portion of the injection needle when in the storage position and the distal-end portion of the injection needle protrudes through a distal-end portion of the cover when the cover is in the administration position,

a coil spring adapted to bias the cover toward the storage position; and

a spring holder adapted to hold the coil spring in a compressed state,

wherein the spring holder includes a hook member adapted to axially hook onto the cover, and

the hook member is configured in such a manner that the coil spring is held in the compressed state between the spring holder and the cover when the hook member is axially hooked on the cover, and, when, after completion of administration of the liquid drug, the syringe barrel is thrust in toward a distal end of the syringe relative to the cover, the hook member and the cover are unhooked such that the coil spring is released and biases the cover toward the storage position,

the present invention proposes a novel hook construction for the spring holder that prevents the coil spring from being released during administration of the liquid drug.

That is, the syringe of the present invention is characterized in that the spring holder is configured to become movable from a hooked position toward the distal end of the syringe relative to the cover, as the syringe barrel is thrust toward the distal end of the syringe relative to the cover after completion of administration of the liquid drug. The hook member is hooked on the cover in the hooked position. Additionally, the cover has an inner periphery including a guide surface adapted, when the spring holder has moved from the hooked position toward the distal end of the syringe relative to the cover, to cause the hook member to radially deform such that the hook member ceases to be hooked on the cover.

In the syringe of the present invention described above, the thrust force during administration of a liquid drug does not act on the spring holder, and the hook member is not unhooked from the cover in an inadvertent manner. When, upon completion of administration of the liquid drug, the syringe barrel is thrust further toward the distal end, the spring holder slightly moves from the hooked position toward the distal end, and this movement causes the hook member to be guided on the guide surface and deformed radially; after this deformation, the hooked state of the hooked member is released such that the coil spring is released. Thereafter, when the thrusting operation for the syringe barrel is halted, the coil spring, now released, biases the cover toward the storage position such that the injection needle is retracted back into the cover.

In the syringe of the present invention, the cover includes, in an integral manner, a cylindrical body adapted to be fitted around the syringe barrel and an inward flange extending radially inwardly from the distal-end portion of the cylindrical body, wherein the cylindrical body includes a support plane facing the distal end of the syringe, the spring holder is located adjacent to an inner periphery of the cylindrical body and rearward of the inward flange, a rear-end plane of the spring holder and a distal-end plane of the syringe barrel face each other in an axial direction so as to abut each other upon completion of administration of the liquid drug, the coil spring is located between the inward flange and the spring holder, the hook member is capable of hooking onto the support plane of the cylindrical body in a direction from the distal end of the syringe and deforming radially inwardly so as to cease to be hooked on the support plane of the cylindrical body. In this construction, when the syringe barrel is further thrust after completion of administration of the liquid drug, the spring holder is pushed by the syringe barrel from the hooked position toward the distal end. Then, the hook member is guided on the guide surface while in abutment and deforms radially inwardly such that the hook member ceases to be hooked on the support plane and thus the coil spring is released.

Effects of the Invention

The syringe of the present invention represents a simple configuration that provides a novel engagement construction where the thrust force during administration of a liquid drug does not act on the hook member of the spring holder and the coil spring is not released in an inadvertent manner during administration.

EMBODIMENTS FOR CARRYING OUT THE INVENTION

FIG. 1shows cross-sectional views of a syringe1according to an embodiment of the present invention during an administration procedure; particularly, the left half of each cross-sectional view shows a longitudinal cross section of a portion of the syringe in which a hook member17bof the spring holder17is present, while the right half shows a longitudinal cross section of a portion in which an elastic engagement member17cof the spring holder17is present. It is also noted that the syringe1of the present embodiment is substantially the same as the syringe disclosed by Patent Document 2 listed above, except for the hooking construction of the hook members of the spring holder; accordingly, the description and drawings of Patent Document 2 are incorporated herein by reference and the inventive syringe will be described using identical reference characters.

The syringe1of the present embodiment includes: a syringe barrel2shaped as a bottomed cylinder and made of transparent or translucent glass or synthetic resin; a gasket3sealingly introduced into the syringe barrel2through the distal-end opening so as to be movable in the axial direction; a plunger4for thrusting the gasket3toward the base end relative to the syringe barrel2; a double-ended injection needle5attached to the plunger4so as to be movable in the axial direction; and a cover6covering the outer periphery of the injection needle5, these components being positioned to be concentric. The gasket3is made of an elastic material, such as rubber.

The cover6includes a cylindrical first cover member14(i.e., cylindrical body) provided with an integral finger-hook flange6alocated on the outer periphery of an intermediate portion thereof as determined along the axial direction, and a second cover member15mounted on and fixed to the distal-end portion of the first cover member14in an integral manner. The syringe barrel2is inserted into the first cover member14through its base-end portion so as to be movable in the axial direction.

The second cover member15includes, in an integral manner, a cylindrical portion adapted to be fitted around the first cover member14, and an inward flange15bextending radially inwardly from the distal-end portion of the cylindrical portion; at the axis center of the inward flange15bis provided a needle retraction hole15a, through which the distal-end portion5bof the injection needle5may be projected and retracted.

Inside the cover6are provided a coil spring16and a spring holder17for holding the spring16while keeping the spring axially compressed. As also shown inFIG. 2, the spring holder17includes a ring portion17apositioned to face the upper plane of the syringe barrel2at the open distal-end portion (i.e., distal-end plane) such that the ring and the plane are arranged in the axial direction, and a hook member17bfor hooking onto the distal-end plane of the first cover member14(i.e., support plane) in the direction from the distal end. A portion of the outer periphery of the hook member17bassociated with the distal end is shaped as an inclined surface to enable smooth guiding by a guide surface S, discussed below, thereby further ensuring that the hook member17bdeforms radially inwardly.

More particularly, a pair of hook members17bare provided to face each other and be arranged across a diameter. Each hook member17bis integral to the ring portion17awith a bent portion f located in between, and includes a hook claw for hooking onto the distal-end plane of the first cover member14(i.e., support plane) in the direction from the distal end. The spring holder17is constructed such that its ring portion17ais positioned adjacent to the inner periphery of the first cover member14and rearward of the inward flange15b, and is axially movable, relative to the cover6and by a small amount, from a hooked position (i.e., position of the spring holder17relative to the cover6as found when the hook members17bare hooked on the distal-end plane of the first cover member14) toward the distal end.

The rear-end plane of the ring portion17aof the spring holder17and the distal-end plane of the syringe barrel2face each other and are arranged in the axial direction, so as to abut each other upon completion of administration of the liquid drug, as shown inFIG. 1(c). The coil spring16is located between the inward flange15band ring portion17a.

Upon completion of administration of the liquid drug, i.e., when the gasket3has just contacted the bottom surface of the syringe barrel2, the hook members17bof the spring holder17are still in engagement with the distal-end plane of the first cover member14, and the distal-end plane of the syringe barrel2and the rear-end plane of the ring portion17aof the spring holder17are in abutment with each other. Upon completion of administration of the liquid drug, when the syringe barrel2is strongly thrust further toward the distal end relative to the cover6against the biasing force of the coil spring16, the gasket3slightly elastically deforms, and thus the spring holder17is moved by the syringe barrel2slightly in the axial direction toward the distal end relative to the cover6, as shown inFIG. 1(c). At this moment, the hook members17bof the spring holder17are guided radially inwardly by a tapered guide surface S provided on the perimeter of the rear side of the inward flange15bsuch that the hook members17bdeform radially inwardly so as to cease to be hooked on the distal-end plane of the first cover member14; the hook members17bare unhooked from the distal-end plane of the first cover member14such that the coil spring16is released.

Then, when the thrusting operation for the syringe barrel2is halted, the biasing force of the coil spring16causes the cover6to axially move toward the distal end relative to the syringe barrel2, as shown inFIG. 1(d), such that the distal-end portion5bof the injection needle5is contained within the cover6.

As shown inFIG. 2, a protrusion18is provided at a predetermined circumferential position on the outer periphery of the ring portion17a(i.e., the same position as each hook member17bin the shown implementation), and a guide groove19is provided on the inner periphery of the first cover member14to extend in the axial direction to allow the associated protrusion18to slide thereon in the axial direction such that the spring holder17is held in the cover6so as to be capable of axially moving and incapable of rotating relative to the cover.

On the inner periphery of the first cover member14are further provided, as also shown in Patent Document 2, a plurality of engagement grooves (indicated by number 20 in Patent Document 2) that extend in the axial direction and are located at predetermined circumferential positions, where a first engagement recess21and a second engagement recess22are provided in each engagement groove to be axially separated from each other. Each of the engagement recesses21and22may be constituted by a through-hole. On the outer periphery of the ring portion17ais provided an elastic engagement member17cto be positioned in a first engagement recess21. A plurality of engagement members17care provided to be circumferentially arranged and correspond to the engagement grooves. Each of the engagement members17chas a base end that is connected to the base-end portion of the ring portion17a, as well as a distal-end portion that is radially expandable and contractable. A stepped portion for engagement is provided on the distal-end portion of the engagement member17c, and the outer periphery of the engagement member17cis an inclined surface that gradually decreases in diameter toward the distal end. When the stepped portions for engagement of the engagement members17cengage those edges of the engagement recesses21and22which are located closer to the distal end, this prevents the first cover member14from moving toward the base end relative to the ring portion17a; on the other hand, when the ring portion17amoves toward the base end relative to the first cover member14, the guiding by the inclined surface causes the engagement members17celastically deform radially inwardly, allowing the spring holder17to slide toward the base end relative to the first cover member14where the engagement members17care guided by the engagement grooves. However, a movement of the ring member17arelative to the first cover member14further toward the base end than the position taken when the engagement members17care in engagement with the second engagement recesses22is prevented by the syringe barrel2, gasket3, plunger4and second cover member15.

The syringe barrel2is filled in advance with a predetermined amount of a liquid drug in a aseptic room, and the gasket3is sealingly introduced into the syringe barrel2so as to seal in the liquid drug. A small indentation2ais provided at the center of the bottom wall of the syringe barrel2. While the syringe disclosed in Patent Document 1 includes an end cap attached to the base-end portion of the syringe barrel, an end cap is omitted in the syringe of the present embodiment in order to reduce the number of components, where the base-end portion itself of the syringe barrel extends toward the axis. Further, while the syringe disclosed in Patent Document 1 includes a stopper attached to the open distal-end portion of the syringe barrel, such a stopper is also omitted according to the present embodiment.

The injection needle5includes a columnar needle base5aand a needle tube extending through the needle base5ain the axial direction. The needle tube protrudes from both ends, as determined along the axial direction, of the needle base5a, where the portion protruding toward the distal end constitutes the distal-end needle portion5b, while the portion protruding toward the base end constitutes the base-end needle portion5c. A sharply cut edge is provided on the tip of each of the needle portions5band5c.

The gasket3is hermetically fitted around the base-end portion of the plunger4. Further, the axis-center portion of the gasket3has a smaller wall thickness so as to be easily pierced through by the base-end portion5cof the injection needle5. As shown inFIG. 1(a), during storage before administration, the base-end portion5cof the injection needle5is separated from the gasket3, located further toward the distal end in the axial direction.

The plunger4is shaped as a hollow cylinder with a bore extending therethrough in the axial direction, and the injection needle5is held by this plunger4.

The plunger4, injection needle5, and cover6constitute a safe operation mechanism for preventing an inadvertent or careless operation to prevent an accident involving the injection needle5. For details about this safe operation mechanism, see description and drawings of Patent Document 2 listed above. The following is some of the main points of the safe operation mechanism cited from Patent Document 2.

The mechanism includes a pair of first elastic engagement members11integral with the cover6and that can be fitted around the needle base5ain the direction from the distal end for holding the injection needle5, and a pair of second elastic engagement members12integral with the plunger4and that can be fitted around the needle base5ain the direction from the base end for holding the injection needle5. Each of the elastic engagement members11and12is shaped as a column with an arc-shaped transverse cross section. The pair of first elastic engagement members11are separated in the circumferential direction and, particularly, positioned to be opposite across a diameter according to the present embodiment. Similarly, the pair of second elastic engagement members12are separated in the circumferential direction and positioned to be opposite across a diameter.

During storage of the syringe1, these first and second elastic engagement members11and12are arranged in the axial direction, and the base-end surface of each of the first elastic engagement members11and the distal-end surface of the corresponding one of the second elastic engagement members12are placed to abut each other and are thus locked in an extended state where the total length of the first and second elastic engagement members11and12is larger than the total length of the injection needle5, thereby preventing the plunger4from being thrust toward the distal end relative to the cover6in the locked position. In this extended state, the distal-end portion5bof the injection needle5is placed within the cover6. On the other hand, when the cover6is rotated relative to the plunger4by 90°, the plurality of second elastic engagement members12face the plurality of spaces defined by the first elastic engagement members11such that the first and second elastic engagement members11and12are arranged alternately in the circumferential direction; by thrusting the plunger4toward the distal end relative to the cover6in this unlocked position, the plurality of first elastic engagement members11alternately engage the plurality of second elastic engagement members12, thereby reducing the total length of the cover6and plunger4. When the total axial length of the cover6and plunger4is thus reduced, the base-end portion5cof the injection needle5pierces through the gasket3and the distal-end needle portion5bprotrudes in the direction of the distal end through the needle retraction hole15aof the cover6.

The first elastic engagement members11are integral with the inward flange15bof the second cover member15of the cover6and extends from the back side of the inward flange15btoward the base end (i.e., downward in the drawings), and the elastic engagement members11are elastically deformable such that their base-end portions (i.e., bottom ends) are expanded in diameter. On the other hand, the second elastic engagement members12extend from an intermediate portion, as determined along the axial direction, of the plunger4toward the distal end (i.e., upward), and elastically deformable such that their distal-end portions (i.e., top ends) are expanded in diameter. The first elastic engagement members11have a larger axial length than the second elastic engagement members12.

The needle base5aof the injection needle5includes a first shaft portion adjacent to the distal end around which the first elastic engagement members11are fitted during storage, a second shaft portion adjacent to the base end around which the second elastic engagement members12are fitted, and a small-diameter shaft portion provided between the first and second shaft portions.

On the outer periphery of the first shaft portion are provided: a pair of restriction ribs arranged opposite in a diametrical direction for abutting edges, as determined along the circumferential direction, of the first elastic engagement members11so as to allow the first elastic engagement members11to rotate up to about 90 degrees relative to the first shaft portion but prevent them from rotating relative to it more than about 90 degrees; and a pair of grooves arranged opposite in a diametrical direction and extending across the entire axial length of the first shaft portion. On the outer periphery of the second shaft portion are provided: four restriction ribs at different circumferential positions for abutting edges, as determined along the circumferential direction, of the second elastic engagement members12so as to prevent the second elastic engagement members12from rotating relative to the second shaft portion; and a pair of grooves arranged opposite in a diametrical direction and extending across the entire axial length of the second shaft portion. These two pairs of grooves are positioned to be displaced in the circumferential direction. Each of the first elastic engagement members11includes a key constituted by a protrusion is provided on the inner surface of the base-end portion, and each of the second elastic engagement members12includes a key constituted by a protrusion provided on the inner surface of the distal-end portion.

In the initial state for storage, the keys are located around the small-diameter shaft portion, where the keys on the first elastic engagement members11engage, in the axial direction, a step between the small-diameter shaft portion and first shaft portion, while the keys on the second elastic engagement members12engage, in the axial direction, a step between the small-diameter shaft portion and second shaft portion, thereby preventing the injection needle5from moving in the axial direction relative to the first and second elastic engagement members11and12. During storage, the keys on the second elastic engagement members12are already positioned to face the grooves on the first shaft portion in the axial direction and, when the first elastic engagement members11are rotated about 90 degrees, the second elastic engagement members12become movable relative to the injection needle5toward the distal end, where the keys move within the grooves in the axial direction. On the other hand, during storage, the keys on the first elastic engagement members11are located about 90 degrees relative to the grooves on the second shaft portion. When the first elastic engagement members11are rotated about 90 degrees relative to the injection needle5, the keys are positioned to face the grooves in the axial direction such that the injection needle5becomes movable relative to the first elastic engagement members11toward the distal end, where the keys move within the grooves in the axial direction.

Further, when, starting with the initial state, the cover6is rotated about 90 degrees relative to the injection needle2and thrust in, the first elastic engagement members11are thrust relative to the injection needle5in the axial direction such that the distal-end portion5bof the injection needle5protrudes from the needle retraction hole15aof the cover6; at this time, the distal-end portions of the restriction ribs on the first shaft portions abut the top plate of the cover6in the axial direction to surround the needle retraction hole15a, thereby making it possible to force the injection needle5to be thrust toward the gasket3toward the base end.

To prevent the cover6from being rotated inadvertently relative to the plunger4from the initial state for storage, the needle base5aof the injection needle5includes a protrusion provided on the outer periphery of the small-diameter shaft portion. When the cover6rotates from the locked position to the unlocked position, each first elastic engagement member11is slightly deformed to be radially expanded and a key climbs over the protrusion. The resistance to the rotating operation represented by this prevents the cover6from being inadvertently rotated.

Further, according to the present embodiment, a cylindrical deformation-prevention part is formed integrally with the plunger. This deformation-prevention part is located closer to the distal end than the second elastic engagement members12are, and are fitted around the plurality of first elastic engagement members11in the initial state for storage to prevent the first elastic engagement members11from being deformed to be radially expanded, thereby preventing the keys on the first elastic engagement members11from being disengaged from the relevant step on the injection needle5. Since the deformation-prevention part is cylindrical in shape, the deformation prevention part constantly prevents the first elastic engagement members11from being deformed to be radially expanded even when the pair of first elastic engagement members11rotate relative to the deformation-prevention part. The inner diameter of the deformation-prevention part is slightly larger than the outer diameter of the pair of first elastic engagement members11to permit the first elastic engagement members11to be slightly deformed to be radially expanded so they can climb over the protrusion.

When the plunger4is thrust toward the distal end relative to the cover6, the distal-end portion of the deformation-prevention part abuts the inward flange15bof the cover6such that the second elastic engagement members12are spaced apart from the inward flange15bby the axial length of the deformation-prevention part. According to the present embodiment, a pair of holding members having an axial length substantially equal to that of the deformation-prevention part extend, between the pair of first elastic engagement members11, from the inward flange15btoward the base end in the axial direction. Each of these holding members has a transverse cross section that is substantially the same as that of the first elastic engagement members11, and the holding members and first elastic engagement members11are arranged alternately so as to be slightly separated in the circumferential direction. The above-discussed spaces for the engagement with the second elastic engagement members12are provided adjacent to the base-end portions of the holding members.

When the first and second elastic engagement members11and12are in the extended state, the holding members are fitted around the outer periphery of the distal-end portion of the needle base5a, but are located closer to the distal end than the distal-end portions of the restriction ribs are, thereby allowing the cover6to be rotated relative to the injection needle5. At this moment, the injection needle5is supported by the cover6at four points, i.e., at the two first elastic engagement members11and two holding members, thereby stabilizing the injection needle5in its held position. On the other hand, when the cover6is rotated from the initial state for storage by 90 degrees and then the plunger4is thrust in relative to the cover6, the injection needle5moves in the axial direction relative to the cover6toward the distal end, and the restriction ribs slide in the axial direction within the slits between the holding members and first elastic engagement members11. At this time, in addition to the four-point support, the engagement of the restriction ribs and the slits further stabilizes the injection needle5in its held position to achieve a yet smoother operation for causing the injection needle5to protrude.

Further, the outer periphery of the deformation prevention part is covered with the first cover member14of the cover6. A pair of recesses are provided that occupy a pair of opposite portions of the deformation prevention part arranged across a diameter and accounting for some of the axial dimension of the deformation prevention part, each recess extending through in a direction perpendicular to the direction of that diameter. Preferably, each recess may be constituted by edges, as determined along the circumferential direction, of a through-hole extending through the deformation prevention part in a radial direction, the edges being in a flat plane extending in that perpendicular direction. On the first cover member14is provided a peephole that, when the cover is in the locked position, faces a recess in the hole's direction of through-extension and, when the cover is in the unlocked position, faces the deformation prevention part. A total of four peepholes are provided, one located on each of the sides of each of the two recesses as determined along the recess's direction of through-extension.

If the plunger4is in a color that is different from those of the other components and thus is conspicuous, e.g., red, the red portions are hardly visible in the peepholes when the cover6is in the locked position, and the peepholes are filled with red when the cover6is rotated to the unlocked position. Thus, the deformation prevention part functions as an indicator that allows the current state of the cover6to be quickly determined by visual inspection.

The present invention is not limited to the above-described embodiment, and can be modified in design as appropriate.