CN113975545A

CN113975545A - Injection head assembly of injector and injector

Info

Publication number: CN113975545A
Application number: CN202111413458.6A
Authority: CN
Inventors: 张明
Original assignee: Beijing Qs Medical Technology Co ltd
Current assignee: Beijing Qs Medical Technology Co ltd
Priority date: 2021-11-25
Filing date: 2021-11-25
Publication date: 2022-01-28
Anticipated expiration: 2041-11-25
Also published as: CN113975545B

Abstract

The invention provides an injection head assembly of an injector and the injector. Wherein the injector head assembly comprises an injector head body, a piston rod component and an end cap. The injector head assembly is configured to be inserted into the distal opening of the syringe body and to a locked position relative to the syringe body. The injector head assembly is configured to: preventing axial separation of the end cap and the injector head body when the distal opening of the syringe body has been inserted but the locked position has not been reached; preventing axial relative displacement of the syringe body and the injector body when the locked position is reached and allowing axial separation of the end cap and the syringe body. The invention avoids taking off the end cap under the condition that the injection head main body is virtually connected at the far end of the injector main body, thereby improving the safety factor of operation. The present invention also provides some preferred arrangements to avoid loss of parts of the injection head assembly, making the operation more hygienic.

Description

Injection head assembly of injector and injector

Technical Field

The present invention relates to a medical device for injecting a liquid drug. More particularly, the present invention relates to an injector head assembly for an injector and an injector. The injector of the present invention may be a needleless injector or a needle injector.

Background

There are syringes of the type comprising a separable injection head and syringe body, the injection head typically in turn comprising an end cap which is removable in use. However, the arrangement of the engagement between the chamber containing the liquid medicine and the end cap is not reasonable enough, and the end cap can be easily disengaged. Such an arrangement presents a certain risk: for example, the user may have removed the end cap and begin a drug aspirating and injection operation when the syringe tip is not properly locked to the body of the syringe, but the injection operation requires high pressure to eject the liquid, which may be accompanied by high pressure. This not only prevents the injection from being carried out, but also can cause injury to the user if the injection head is ejected at high pressure.

Accordingly, there is a need to provide an injector head assembly for an injector and an injector that at least partially address the above problems.

Disclosure of Invention

In order to overcome the above disadvantages, an injection head assembly for an injector, an injector body and an injector are proposed according to the present invention. The engagement structure between the end cap and the syringe body is constrained so that the end cap and the syringe body remain engaged continuously until the injector head assembly of the present invention is properly installed in a locked position relative to the syringe body, thereby avoiding removal of the end cap in the event that the injector head body is virtually attached to the distal end of the syringe body and increasing the safety factor of operation.

In addition, the present invention provides that in the event that the syringe body and the syringe body are in correct locking engagement and the end cap has been removed, the syringe body cannot be rotated relative to the syringe body towards the unlocked position. To remove the injector head body, the end cap must be reinstalled and the injector head assembly removed in its entirety. Such an arrangement can avoid loss of parts of the injection head assembly, making the operation more hygienic.

In the present invention, the engagement between the piston rod member and the syringe body is also more rational, and the engagement between the piston rod member and the syringe body can be allowed to unlock the engagement between the piston rod member and the syringe body without manual operation by the user.

The syringe body of the present invention provides a viewing window for the user to view the contents of the vial and allows relative axial movement between the outer housing and the inner ram while preventing relative rotation. These arrangements can both improve the accuracy and convenience of operation.

According to one aspect of the present invention there is provided an injector head assembly for a syringe, the syringe having a syringe body, the injector head assembly being configured to be mountable to a distal end of the syringe body, the injector head assembly comprising:

the injection head comprises an injection head main body, wherein a cavity with an open near end is arranged in the injection head main body, and a micropore for communicating the cavity with the outside is arranged at the far end of the injection head main body;

a piston rod component having a distally extending piston rod, the piston rod component disposed proximal to the injector head body and enabling the piston rod to extend into the cavity;

an end cap mounted at a distal end of the injector head body,

wherein the injection head assembly is configured to be insertable into the distal opening of the syringe body to a locked position relative to the syringe body,

and, the injector head assembly is configured to: preventing axial separation of the end cap and the injector head body when the distal opening of the syringe body has been inserted but the locked position has not been reached; preventing axial relative displacement of the injector head body and the syringe body and allowing axial separation of the end cap and the injector head body when the locked position is reached.

In one embodiment, the end cap and the injector head body are engaged by a first set of mating structures, the first set of mating structures being transformable between an engaged state such that the injector head body and the end cap are axially fixed together and a disengaged state such that the injector head body and the end cap are axially separated,

wherein the first set of mating structures is transitionable from the engaged state to the disengaged state in response to free-hand manipulation by an operator when the injection head assembly is not inserted into the distal opening of the syringe body; when the injector head assembly has been inserted into the distal opening of the syringe body but has not reached the locked position, the first set of mating structures is constrained by the syringe body from transitioning from the engaged state to the disengaged state.

In one embodiment, the end cap and/or the injector head body are deformed to enable the first set of mating structures to transition between the engaged state and the disengaged state, and the injector body constrains the end cap and/or the injector head body from deforming when the injector head assembly has been inserted into the distal opening of the injector body but has not reached the locked position.

In one embodiment, the first set of mating structures includes:

an arm located on the end cap and extending proximally from the body of the end cap, a first protrusion being disposed radially inward of a proximal end of the arm; and

a first mating feature on the injector head body, a small step disposed at a distal end of the first mating feature,

wherein the small step is distal to the first protrusion when the first mating feature set is in the engaged state; the first projection passes over the small step during transition of the first mating structure set from the engaged state to the disengaged state.

In one embodiment, the arms are deformable radially outwardly to cause the first projection to axially clear the small step,

and the arms are constrained from deforming radially outward by the syringe body when the syringe head assembly has been inserted into the distal opening of the syringe body but has not reached the locked position.

In one embodiment, the injector head assembly is configured to: the distal end face of the syringe body to which it is applied is provided with an elastic member slightly protruding from the distal end face, and

the injector head body is provided with a circumferentially extending flange that is intermittently disposed and defines the first mating feature at the discontinuity, the arm and the flange together defining a circumferentially fully extending boss that is configured to compress the resilient member proximally to bring a distal face of the resilient member and a distal face of the syringe body into alignment, and the arm presses against the resilient member when the injection head assembly is in the locked position.

In one embodiment, a resilient member is mounted at a distal location inside the end cap, and the first set of mating structures is configured to allow a small amount of axial movement between the end cap and the injector head body such that the resilient member is compressed by the distal end of the injector head body when the injector head body and the end cap are engaged.

In one embodiment, the injector head body and the syringe body are locked therebetween by a second set of mating structures that limit relative axial movement between the injector head body and the syringe body.

In one embodiment, the second set of mating structures includes:

second protrusions provided intermittently in a circumferential direction on an inner side surface of the syringe body; and

a second mating feature formed on an exterior side of the injector head body, the second mating feature defined by flanges located on axial sides of the second mating feature, respectively,

wherein, during mounting of the injector head assembly to the syringe body, the proximal flange defining the second mating feature is axially passable through the discontinuity of the second protrusion to insert the injector head assembly into the distal opening of the syringe body, whereupon rotation of the injector head assembly relative to the syringe body causes the second protrusion to enter the second mating feature.

In one embodiment, the injector head assembly is in a first transition position when inserted into the distal opening of the syringe body, the injector head assembly being rotatable relative to the syringe body in a mounting rotational direction from the first transition position to the locked position, the injector head assembly being configured to be restricted from continued proximal movement relative to the syringe body in the first transition position but to allow distal movement of the injector head assembly as a whole relative to the syringe body.

In one embodiment, the injector head body is locked to the outer housing of the injector body when in the locked position, and there is also a second transition position between the first transition position and the locked position, the injector head assembly being configured to: in the second transition position, the piston rod member is locked to an inner ram of the syringe body that is axially movable relative to the outer housing and is disengaged from the injector head body as the injector head body continues to rotate in the mounting rotational direction.

In one embodiment, the piston rod part and the injector head body are mated by a third set of mating structures configured to limit axial relative movement and relative rotation between the piston rod part and the injector head body below a first predetermined torque,

and, a fourth set of mating structures between said piston rod member and said inner ram, said fourth set of mating structures configured to limit axial relative movement and relative rotation between said piston rod member and said inner ram at less than a second predetermined torque,

wherein the first predetermined torque is less than the second predetermined torque.

In one embodiment, the third set of mating structures includes:

a distally extending third protrusion provided on the piston rod member, a catch being provided radially inside the third protrusion;

a third mating feature disposed on the injector head body, the third mating feature comprising:

a mating groove;

a hook mating portion formed at a proximal end of the mating groove, the hook mating portion and the hook engaging to limit proximal movement of the piston rod component relative to the injector head body;

a stopper formed on an upstream side of the fitting groove in the mounting rotation direction, the stopper blocking the third protrusion to prevent the piston rod member from rotating in the mounting rotation direction with respect to the injector head main body;

a small projection formed on a downstream side of the fitting groove in the mounting rotation direction, the small projection being sized so that the third projection can pass over the small projection under an action equal to or greater than the first predetermined torque.

In one embodiment, the fourth set of mating structures includes: a radially protruding fourth boss formed at a proximal end of the piston rod member; and a fourth mating feature formed on the inner ram.

In one embodiment, a radial inner side of the injector head body is provided with a first safety projection, a radial outer side of the piston rod component is provided with a second safety projection corresponding to the first safety projection, and the first safety projection and the second safety projection are configured to: in the event that the plunger rod component has disengaged from the injector head body but has not yet fully engaged the internal ram, the first relief projection can interfere with the second relief projection to facilitate engagement of the plunger rod component with the internal ram.

In one embodiment, the piston rod member comprises:

a mounting base including a radially outwardly projecting wing, the piston rod extending distally from the mounting base;

a cylindrical structure extending proximally from the mounting base, the fourth protrusion being formed at a proximal end of the cylindrical structure.

In one embodiment, the injector head body comprises:

a cavity portion for receiving the piston rod of the piston rod assembly;

a first mating feature proximal to the cavity portion and for engaging the end cap;

a second mating feature proximal to the first mating feature for engagement with the syringe body;

a third mating feature located proximal to the second mating feature and adapted to engage the piston rod component.

In one embodiment, the piston rod member comprises:

a piston rod mounting base;

the piston rod extending distally from the mounting base;

a catch portion extending distally from a distal end of the mounting base for mating with the third mating feature, a projection being disposed radially inward of the catch portion; and

a projection radially outward of the proximal end of the mounting base configured for engagement with the syringe body.

According to another aspect of the present invention, there is provided a syringe comprising:

a syringe body having an outer housing and an inner ram located within the outer housing and axially movable relative to the outer housing;

an injector head assembly configured to be mountable to the syringe body, the injector head assembly comprising:

an end cap disposed at a distal end of the injector head body,

wherein the injection head assembly is insertable into the distal opening of the syringe body to a locked position relative to the syringe body,

and, the syringe is configured such that: preventing axial separation of the end cap and the injector head body when the injector head assembly has been inserted into the distal opening of the syringe body but has not reached the locked position; preventing axial relative displacement of the injector head body and the outer housing and allowing axial separation of the end cap and the injector head body when the injector head assembly is in the locked position.

wherein the first set of mating structures is transitionable from the engaged state to the disengaged state in response to free-hand manipulation by an operator when the injection head assembly is not inserted into the distal opening of the injector body; when the injector head assembly has been inserted into the distal opening of the syringe body but has not reached the locked position, the first set of mating structures is constrained by the syringe body from transitioning from the engaged state to the disengaged state.

In one embodiment, the end cap is deformable radially outwardly to enable the first set of mating structures to be transitioned between the engaged state and the disengaged state, and the injector head assembly is rotated to the locked position upon insertion into the distal opening of the syringe body,

wherein the inner diameter at the distal location of the outer housing is set to: the inner surface of the outer housing and the outer surface of the end cap are in contact when the injection head assembly is inserted into the distal opening of the syringe body but not rotated to the locked position; when the injection head assembly is in the locked position, a radial gap exists between the inner surface of the outer housing and the outer surface of the end cap, the radial gap providing room for radial deformation of the end cap.

In one embodiment, the first set of mating structures includes:

an arm located on the end cap and extending proximally from the body of the end cap, the arm having a first protrusion disposed on an inner side of a proximal end thereof; and

a first mating feature on the injector head body, a small step distal to the first mating feature,

In one embodiment, the arms are deformable radially outwardly to enable the first projection to pass over the small step,

and, the inner diameter at the distal location of the outer housing is set to: when the injection head assembly is inserted into the distal opening of the syringe body but not rotated to the locked position, the inner surface of the outer housing and the outer surface of the arm are in contact; when the injection head assembly is in the locked position, a radial gap exists between the inner surface of the outer housing and the outer surface of the arm, the radial gap providing room for radial deformation of the arm.

In one embodiment, the distal end face of the outer housing of the syringe body is provided with an elastic member slightly protruding from the distal end face, and

the injector head body is provided with a circumferentially extending flange that is intermittently disposed and defines the first mating feature at the discontinuity, and the arm and the flange together define a circumferentially fully extending boss that is configured to compress the resilient member proximally to bring a distal face of the resilient member and a distal face of the outer housing into alignment, and the arm presses against the resilient member when the injection head assembly is in the locked position.

In one embodiment, a resilient member is mounted at the distal end of the interior of the end cap, and the first set of mating structures is configured to allow a small amount of axial movement between the end cap and the injector head body, such that the resilient member is compressed by the distal end of the injector head body when the injector head body and the end cap are engaged.

In one embodiment, the injector head body and the injector body are locked together by a second set of mating structures, the second set of mating structures comprising:

second protrusions provided intermittently in a circumferential direction on an inner side surface of the outer case; and

wherein during mounting of the injector head assembly to the syringe body, the proximal flange defining the second mating feature is axially passable through the discontinuity of the second protrusion, and the injector head assembly is subsequently rotated relative to the syringe body such that the second protrusion enters the second mating feature.

In one embodiment, there is also a second transition position between the first transition position and the locking position, the injection head assembly being configured to: the plunger rod component and the internal ram lock at the second transition position and disengage from the injector head body as the injector head body continues to rotate in the installation rotational direction.

In one embodiment, the third set of mating structures includes:

a mating groove;

a small projection formed on a downstream side of the fitting groove in the mounting rotation direction, the small projection being sized so that the third projection can pass over the small projection under an action of the first predetermined torque or more, thereby disengaging the injector head body and the piston rod member.

In one embodiment, the piston rod member comprises:

a cylindrical structure extending proximally from the mounting base, the fourth protrusion being formed at a proximal end of the cylindrical structure,

and, the internal thrust rod is provided with a step that can abut against a proximal side of the mounting base, the step being shaped and the wing panel but having a circumferential dimension that is slightly larger than a circumferential dimension of the wing panel to allow the piston rod component to be rotatable relative to the internal thrust rod between the first and second transitional positions.

In one embodiment, the step is defined by circumferential blocks at both circumferential ends thereof, the circumferential blocks being capable of pushing the wings in a rotational direction to force the rod part into engagement with the internal ram during installation and the rod part into engagement with the injector head body during unloading.

In one embodiment, the injector head body comprises:

a cavity portion for receiving the piston rod of the piston rod assembly;

a second mating feature proximal to the first mating feature for engaging the outer housing;

In one embodiment, the piston rod member comprises:

a piston rod mounting base;

the piston rod extending distally from the mounting base;

a projection radially outward of the proximal end of the mounting base configured for engagement with the internal pushrod.

In one embodiment, the inner ram is configured to receive a drug storage vial therein, and the outer housing and the inner ram are provided with a viewing window for an operator to view the drug storage vial at a position axially aligned with the drug storage vial.

In one embodiment, the viewable window is configured to:

a plurality of hollows formed on the inner push rod spaced apart in a circumferential direction, each of the hollows being formed in an elongated shape extending in an axial direction; and

the shell comprises a plurality of transparent parts formed on the outer shell, and the positions of the transparent parts and the positions of the hollow parts are in one-to-one correspondence.

In one embodiment, one of the inner surface of the outer housing and the outer surface of the inner thrust rod is provided with an anti-rotation projection extending in the axial direction, and the other of the inner surface of the outer housing and the outer surface of the inner thrust rod is provided with a keyway corresponding to the anti-rotation projection, the anti-rotation projection and the keyway cooperating to prevent relative rotation between the outer housing and the inner thrust rod but permit relative axial movement between the outer housing and the inner thrust rod.

Drawings

For a better understanding of the above and other objects, features, advantages and functions of the present invention, reference should be made to the preferred embodiments illustrated in the accompanying drawings. The same or similar reference numbers in the drawings refer to the same or similar parts. It will be appreciated by persons skilled in the art that the drawings are intended to illustrate preferred embodiments of the invention without any limiting effect on the scope of the invention, and that the various components in the drawings are not drawn to scale.

FIG. 1 is a perspective view of a syringe according to a preferred embodiment of the present invention, with partial structure at the proximal end of the syringe omitted;

FIG. 2 is an exploded view of the syringe of FIG. 1;

FIG. 3 is an exploded view of the injector head assembly of FIG. 2, but in a top-down orientation in the drawing plane opposite that of FIG. 2;

FIG. 4 is an assembled schematic view of the injector head assembly of FIG. 2, with the piston rod component engaged with the injector head body;

FIG. 5 is a schematic view of the cross-sectional view of FIG. 4;

FIG. 6 is an assembled schematic view of the syringe head assembly of FIG. 2, with the engagement between the piston rod component and the syringe head body disengaged;

fig. 7A-15B show perspective views of various stages in the use of the syringe shown in fig. 1.

Detailed Description

Hereinafter, a syringe body and an injection head of the syringe according to the present invention will be described in detail with reference to the accompanying drawings. The following is given only by way of preferred embodiments according to the invention, and other ways of carrying out the invention will be apparent to those skilled in the art on the basis of the preferred embodiments, and are within the scope of the invention.

The invention provides an injection head assembly of an injector and the injector. First, it should be noted that the terms of direction and position of the present invention should be understood as relative direction and relative position. The directional terms, positional terms, etc. referred to herein may be understood with reference to the drawings, for example, the "axial direction", etc. referred to herein may be understood as a direction along or parallel to the X-X direction in the drawings; references herein to "radial", "radial direction", "circumferential direction" and the like are directions with respect to the X-X axis; reference to "direction of rotation" in the context of the present invention is to be understood as a direction of rotation about the X-X axis, which is substantially equivalent to "circumferential direction". References herein to "proximal", "proximal direction", etc., are to directions closer to the operator in a direction along or parallel to axis X-X (considering the operator holding the injector for aspiration and injection); as used herein, "distal" and "distal direction" refer to a direction along or parallel to the axis X-X away from the operator and also to the direction in which the fluid is ejected during the injection step. The terms "proximal", "distal" and "distal" used herein refer to an end cap, wherein one end of the end cap is distal and the other end distal to the end cap is proximal.

Figures 1-15B illustrate a syringe and injector head assembly according to some preferred embodiments of the present invention. Although fig. 1-15B illustrate a needle-free injector, needle-free injector head assembly, it is to be understood that the present invention is applicable to needle injectors, needle injector head assemblies. The invention achieves accurate dosing by pre-introducing the liquid to be injected into a chamber within the injector head body (i.e., a drug aspiration step as will be described later), and such injectors and injector head assemblies can be used for both needle-free and needle-injection. Further, the injector and the injection head assembly of the invention can also realize the switching of the needle and the needle-free injection mode. For example, the injection mode of the syringe can be switched from a needleless injection to a needle injection by attaching an injection needle to the injection hole of the injection head. And corresponding to the needle injection head assembly, the end cap may be provided to have a long size to enclose a portion of the injection head body and the needle coupled to the front end of the injection head body therein, and the end cap does not interfere with the needle.

Referring to fig. 1 and 2, the syringe 1 includes a syringe body 100 and an injection head assembly 200. The syringe body 100, in turn, includes an outer housing 110 and an inner ram 120 located within the outer housing 110 and axially movable relative to the outer housing 110. The injection head assembly 200 can be mounted at the distal end of the syringe body 100. Figures 3-6 illustrate some detailed preferred arrangements of the injector head assembly 200 of figures 1-2.

Referring to fig. 3, injection head assembly 200 includes an injection head body 210, a piston rod member 220 attached to a proximal side of injection head body 210, and an end cap 230 attached to a distal side of injection head body 210. A cavity 210c with an open proximal end is arranged in the injector head body 210, and a micropore for communicating the cavity 210c with the outside is arranged at the distal end of the injector head body 210. The piston rod member 220 has a distally extending piston rod 220a, the distal end of the piston rod 220a being a piston 220 b. Plunger rod component 220 is disposed proximal to injector head body 210 and enables plunger rod 220a to extend into cavity 210 c.

Injector head body 210 and end cap 230, and injector head body 210 and piston rod assembly 220 are detachably coupled. And, in the process of the injection head assembly 200 being mounted to the syringe body 100: preventing axial separation of end cap 230 and syringe head body 210 until a locked position is reached; in the locked position, prevents axial relative displacement of injector head body 210 and syringe body 100 and allows axial separation of end cap 230 and injector head body 210.

In this embodiment, in the process of mounting the injection head assembly 200 to the syringe body 100, the injection head assembly 200 is inserted into the distal end of the syringe body 100 in the proximal direction (the position of the injection head assembly 200 relative to the syringe body 100 at this time is referred to as a first transition position), and then the injection head assembly 200 is rotated in a rotation direction (which is referred to as a mounting rotation direction R1) to a locking position of the injection head body 210 of the injection head assembly 200 relative to the syringe body 100; when it is desired to unload injector head assembly 200 from injector body 100, injector head assembly 200 is first rotated in another rotational direction opposite mounting rotational direction R1 (referred to as unloading rotational direction R2) to a first transition position, and then injector head assembly 200 is moved in a distal direction to disengage from injector body 100.

Preferably, a stop structure is correspondingly provided in the syringe body 100 to be able to axially stop the injection head assembly 200 at the first transition position. That is, when the injection head assembly 200 is in the first transition position, it cannot continue to move proximally relative to the syringe body 100, but allows the injection head assembly 200 as a whole to move distally relative to the syringe body 100.

Wherein, when injector head assembly 200 is in the locked position, injector head body 210 is locked to outer housing 110 of syringe body 100 and piston rod assembly 220 is locked to inner ram 120 of syringe body 100.

In this embodiment, the end cap 230 and the injector head body 210 are coupled by a first set of mating structures, the injector head body 210 and the outer housing 110 are coupled by a second set of mating structures, the injector head body 210 and the piston rod assembly 220 are coupled by a third set of mating structures, and the piston rod assembly 220 and the inner ram 120 are coupled by a fourth set of mating structures. Each mating structure group includes some engagement structures disposed on two corresponding components of the mating structure group, and each mating structure group is capable of restricting a specific relative movement between the two corresponding components of the mating structure group. Each of the mating structure groups will be described in detail in turn.

Referring to fig. 3, the first set of mating structures includes an arm 232 on the endcap 230 and extending proximally from the body 231 of the endcap 230 and a first mating feature 211 (i.e., a first mating location) on the injector head body 210. The proximal inside of the arm 232 is provided with a first protrusion 233 and the distal end of the first mating feature 211 is provided with a small step 2111. The first set of mating structures is shiftable between an engaged state axially securing injector head body 210 and end cap 230 together and a disengaged state axially separating injector head body 210 and end cap 230. The state shown in fig. 3 corresponds to the separated state of the first mating structure group, and the states shown in fig. 4 and 5 correspond to the engaged state of the first mating structure group. An orientation indicator 234 is also provided on the body 231 of the end cap 230.

In particular, the arms 232 are deformable radially outwardly to allow the first protrusions 233 to clear the small step 2111 to transition the first set of mating structures between an engaged state and a disengaged state. The first mating feature set is transitionable from the engaged state to the disengaged state in response to free-hand manipulation by an operator when the injection head assembly 200 is not mounted to the syringe body 100; when syringe head assembly 200 has been inserted into the distal end of syringe body 100 but has not reached the locked position (i.e., during rotation from the first transitional position to the locked position), arms 232 are constrained from deforming radially outward by outer housing 110, at which point the first set of mating structures cannot be transformed from the engaged state to the disengaged state. While when injection head assembly 200 is in the locked position, arms 232 are allowed to deform radially outward, at which point the user can actuate end cap 230 distally to disengage it from injection head body 210.

An assembled view of injection head assembly 200 is shown in fig. 4 with the first set of mating structures in an engaged state and with arms 232 of end cap 230 seated within first mating features 211 of injection head body 210. Preferably, injector head body 210 is provided with a circumferentially extending flange 214, flange 214 is intermittently provided and defines first mating feature 211 at the discontinuity, and the proximal ends of arms 232 and flange 214 together define a boss that extends completely in the circumferential direction. This circumferential ledge serves to compress resilient member 112 provided at the distal face of syringe body 100 to limit movement of syringe body 210 in the unlocking direction when syringe body 210 is locked to outer housing 110 and end cap 230 has been removed. The number of the elastic members 112 is preferably two, and may be one, three or more.

Preferably, referring to fig. 5, the resilient plug 235 is mounted at a distal location on the interior of the end cap 230, and the first set of mating structures is configured to allow a small amount of axial movement between the end cap 230 and the injector head body 210, such that the resilient plug 235 is compressed by the distal end of the injector head body 210 when the injector head body 210 and end cap 230 are engaged. Such an arrangement can enhance the sealing effect of the injection head assembly 200 and also ensure a tight engagement between the components of the injection head assembly 200 in the assembled state.

Referring to fig. 3-5, 7A, the set of mating structures between the syringe body 100 and the outer housing 110, i.e., the second set of mating structures, includes: second protrusions 111 intermittently provided circumferentially on the inside face of syringe body 100, and second mating features 212 (i.e., second mating locations) formed on the outside face of injector head body 210. Second mating feature 212 is defined by

flanges

215, 214, respectively, on either axial side of second mating feature 212, and the second set of mating structures limit relative axial movement between injector head body 210 and injector body 100.

During mounting of the injection head assembly 200 to the syringe body 100, the proximal flange 215 defining the second mating feature 212 can pass axially over the discontinuity of the second protrusion 111 to bring the injection head assembly 200 to the first transition position, and then the injection head assembly 200 is rotated relative to the syringe body 100 such that the second protrusion 111 enters the second mating feature 212. Also, the downstream end of the second mating feature 212 in the installation rotational direction R1 is provided with a stop protrusion 217 extending axially such that when the injector head body 210 is rotated in the installation rotational direction R1 to a locked position, the stop protrusion 217 interferes with the second protrusion 111 to limit continued rotation of the injector head body 210 in the installation rotational direction R1.

Unlike the first mating structure, which is capable of changing state in response to freehand actuation by an operator, the second set of mating structures is relatively firmly engaged. If the second engagement structure group is to be disengaged, it is necessary to operate according to the correct unloading process, for example, first mounting the end cap 230 to the syringe body 100, and then integrally rotating the end cap 230 and the syringe body 100 in the unloading rotation direction R2. Injector head body 210 and outer housing 110 do not separate from one another under direct axial forces only, which would tend to disable the second mating feature set. Thus, when injection head assembly 200 is mounted to the locked position, the operator can actuate end cap 230 distally to remove it, an operation that does not interfere with the locking engagement between injection head body 210 and outer housing 110.

On the other hand, in the present embodiment, there is also a second transition position between the first transition position and the lock position. In the second transition position, the piston rod member 220 and the internal ram 120 are lockingly engaged to disengage the syringe body 210 as the syringe body 210 continues to rotate in the installation rotational direction R1. Correspondingly, some preferred arrangements of some engagement structures associated with the piston rod member 220 are also provided in this embodiment.

The set of mating structures between piston rod part 220 and injector head body 210, i.e. the third set of mating structures, is configured to limit axial relative movement and relative rotation between piston rod part 220 and injector head body 210 below a first predetermined torque, e.g. a torque acting on piston rod part 220 or injector head body 210 to rotate them relative to each other. The set of mating structures between the piston rod member 220 and the inner push rod 120, i.e., the fourth set of mating structures, is configured to limit axial relative movement and relative rotation between the piston rod member 220 and the inner push rod 120 to less than a second predetermined torque, e.g., a torque acting on the piston rod member 220 or the inner push rod 120 to rotate them relative to each other.

Wherein the first predetermined torque is less than the second predetermined torque. The arrangement is such that when injector head assembly 200 is rotated as a whole to the second transitional position, at which point injector head body 210, internal ram 120 and piston rod assembly 220 are in locking engagement, a force in the installation rotational direction R1 continues to be applied to injector head body 210, and when the force reaches the first predetermined torque, relative rotation occurs between injector head body 210 and piston rod assembly 220, while at this point the relative torque between piston rod assembly 220 and internal ram 120 has not yet reached the second predetermined torque, and engagement between piston rod assembly 220 and internal ram 120 is maintained. That is, when injector head assembly 200 is rotated to the second transition position, piston rod member 220 no longer continues to rotate.

In particular, referring to fig. 3-6, the third set of mating structures includes a distally extending third protrusion 221 provided on the piston rod member 220 and a third mating feature 213 (i.e., a third mating location) provided on the injector head body 210. The distal side of the mounting portion of the piston rod member 220 located on the distal side of the piston rod 220a is provided with an annular extension 225, a third projection 221 extends distally from the extension 225, and the third projection 221 is flush with the radially outer surface of the extension 225. A hook is disposed on the radial inner side of the third protrusion 221. The third mating feature 213 includes: the engaging groove, the hook engaging portion 216 formed at the proximal end of the engaging groove, the stopper 218a formed on the upstream side in the mounting rotation direction R1 of the engaging groove, and the small projection 218 formed on the downstream side in the mounting rotation direction R1 of the engaging groove. The catch mating portion 216 engages with the radially inner catch of the third protrusion 221 to limit proximal movement of the piston rod assembly 220 relative to the syringe body 210. The stopper 218a blocks the third protrusion 221 to prevent the piston rod member 220 from rotating relative to the syringe main body 210 in the mounting rotation direction R1. Small protrusion 218 is dimensioned such that third protrusion 221 is able to ride over the small protrusion under an action of equal to or greater than a first predetermined torque, thereby disengaging injector head body 210 and piston rod assembly 220. Fig. 6 shows the situation after the third protrusion 221 has passed the small protrusion 218, when the third set of mating structures has been in engaging contact.

The fourth set of mating structures includes a radially protruding fourth protrusion 222 formed on the proximal end of the piston rod member 220 and a fourth mating feature 123 formed on the inner push rod 120 (i.e., a fourth mating position, see fig. 7B). Preferably, the piston rod member 220 further comprises a cylindrical structure 223 extending proximally from the mounting base, the fourth protrusion 222 being formed at a proximal end of the cylindrical structure 223. The cylindrical structure 223 is provided with a plurality of axially extending slots distributed circumferentially, which allows the proximal end of the cylindrical structure 223 to be slightly deformed to urge the fourth protrusion 222 into the fourth mating feature 123.

In some cases, when the injection head assembly 200 is inserted into the syringe body 100, the fourth protrusion 222 may contact with the inner wall of the inner shaft 120, and due to the elastic deformation, a friction force (the magnitude of the friction force is related to the interference of the fourth protrusion 222 with the mating portion of the inner shaft 120) may be formed between the fourth protrusion 222 and the inner wall of the inner shaft 120, and when the torque generated by the friction force is greater than the first predetermined torque, the piston rod member 220 cannot rotate synchronously with the inner shaft 210, so that the fourth protrusion 222 cannot reach the fourth mating feature 123, and the engagement effect of the piston rod member 220 and the inner shaft 120 is affected. To ensure the effectiveness of the fourth set of mating structures, a first tapered protrusion 219 (i.e., a first relief protrusion) near the proximal end of the radially inner side of the injector head body 210, and a second tapered protrusion 220c (i.e., a second relief protrusion) corresponding to the first tapered protrusion 219 is provided on the radially outer side of the piston rod 220 a. The radial dimensions of both the first conical projection 219 and the second conical projection 220c taper distally. Only one first tapered protrusion 219 may be provided or two first tapered protrusions 219 may be provided symmetrically with respect to the axis. Due to the first and second

tapered protrusions

219 and 220c, when the injector head assembly 200 is twisted towards the locked position, even if the piston rod member 220 cannot rotate synchronously with the internal push rod 210, when the injector head body 210 is twisted with the end cap 230 to a certain angle, the first tapered protrusion 219 interferes with the second tapered protrusion 220c to push the piston rod member 220 to twist until the fourth protrusion 222 reaches a position to properly engage the fourth mating feature 123.

As can be seen by referring to fig. 2 in conjunction with the above description, the injector head body 210 is provided with a first mating feature set (i.e., the first mating feature 211), a second mating feature set (i.e., the second mating feature 212), and a third mating feature set (i.e., the third mating feature 213). Injector head body 210 further includes a cavity portion 210a for receiving piston rod 220a of piston rod assembly 220 and a body mounting base 210b located proximal to cavity portion 210 a. The first mating feature 211, the second mating feature 212, and the third mating feature 213 are located on the body mounting base 210 b. Also, the second mating feature 212 is located proximal to the first mating feature 211, and the third mating feature 213 is located proximal to the second mating feature 212. The piston rod member 220 is provided with a third protrusion (i.e. a third protrusion 221) of the third mating structure group and a fourth protrusion (i.e. a fourth protrusion 222) of the fourth mating structure group, the piston rod member 220 further includes a piston rod mounting base 224 and a piston rod 220a extending distally from the piston rod mounting base 224, the third protrusion of the third mating structure group is formed on a radially inner side of a hook portion extending distally from a distal end of the mounting base, and the fourth protrusion of the fourth mating structure group is located on a radially outer side of a proximal end of the mounting base.

Preferably, referring back to fig. 4-6, piston rod mounting base 224 in turn includes a pair of opposing wings 224b (the number of wings may be one, three, or more in other embodiments) that project radially outward, with piston rod 220a extending distally from the mounting base. Correspondingly, steps 1211 (see fig. 7B) are formed in the outer housing 110 corresponding to the pair of wings 224B, the steps 1211 being capable of abutting against the proximal side of the wings 224B to limit further proximal movement of the injection head assembly 200 at the first transition position. The step 1211 may constitute the aforementioned "stopper structure". The shape of step 1211 and wing plate 224b are adapted but the circumferential dimension of step 1211 is slightly larger than the circumferential dimension of wing plate 224b to allow piston rod member 220 to be rotatable relative to inner pushrod 120 between the first transition position and the second transition position.

Specifically, the step portion 1211 is discontinuous in the circumferential direction, and is two sectors spaced apart in the circumferential direction in the present embodiment, and at least two portions formed in another shape spaced apart in the circumferential direction may be provided in other embodiments. The structure defined at both circumferential ends of the step portion 1211 is a circumferential block 1212 (see fig. 7B), the circumferential block 1212 protrudes radially inward with respect to the step portion 1211, and the circumferential block 1212 can push the wing plate 224B in the rotational direction, thereby functioning as a safety in both cases:

first, when the injector head assembly 200 is rotated in the mounting rotation direction R1: if, during rotation of injector head body 210 from the second transitional position toward the locked position, plunger rod component 220 were to inadvertently not disengage from injector head body 210 but instead tended to continue to rotate with injector head body 210 (i.e., tended to disengage from inner ram 120), circumferential block 1212 would act as a stop for wing 224b, preventing further rotation of plunger rod component 220 to ensure that plunger rod component 220 would remain properly engaged with inner ram 120;

second, when the syringe head assembly 200 is rotated in the unlocking rotation direction R2: if, during rotation of injector head body 210 from the locked position to the second transitional position, third protrusion 221 were accidentally unable to pass over small protrusion 218 and thereby be unable to enter third mating feature 213, it would result in plunger rod assembly 220 not being integrally engaged with injector head body 210 and end cap 230 and thus possibly not being removed from syringe body 100 along with injector head body 210 and end cap 230, in which case circumferential block 1212 would also act to push against wing 224b, pushing plunger rod assembly 220 into proper engagement with injector head body 210, thereby ensuring that injector head assembly 200 could be removed as a unit.

It will be appreciated from the foregoing description that the syringe body 100 also has some preferred arrangements. For example, turning back to fig. 2, an elastic member 112 formed as an elastic column is provided on the distal end face of the outer housing 110, the elastic member 112 slightly protruding from the distal end face. A second projection 111 is provided near the distal end of the radially inner side of the outer housing 110, the second projection 111 constituting a part of the second fitting structure group. The second projections 111 are intermittently circumferentially arranged to allow a proximal flange of the injection head assembly 200 defining the second mating feature 212 to axially pass the discontinuities of the second projections 111. The inner push rod 120 is provided with a fourth mating feature 123 near its distal end, the fourth mating feature 123 constituting part of a fourth set of mating structures.

Preferably, the inner pushrod 120 includes an axially extending pushrod body 122 and an annular mounting portion 121 at a distal end of the pushrod body, the annular mounting portion 121 having a radial dimension greater than that of the pushrod body 122. The inner ram 120 can be used to house a drug storage vial, and the outer housing 110 and inner ram 120 are provided with a viewing window for an operator to view the drug storage vial at a position axially aligned with the drug storage vial. The visible window is configured as a plurality of hollowed-out portions 124 formed on the inner push rod 120 spaced in a circumferential direction and a plurality of transparent portions 113 formed on the outer housing 110. Each hollowed-out portion 124 is formed in an elongated shape extending in the axial direction; the positions of the transparent parts 113 and the hollow parts 124 correspond to each other one by one.

Also preferably, the inner surface of the outer housing 110 is provided with an anti-rotation protrusion (not visible in the view of the drawings) extending in an axial direction, and the other of the outer surfaces of the inner thrust rod 120 is provided with a keyway 125 corresponding to the anti-rotation protrusion, the anti-rotation protrusion and keyway 125 cooperating to prevent relative rotation between the outer housing 110 and the inner thrust rod 120, but to allow relative axial movement between the outer housing 110 and the inner thrust rod 120.

Fig. 7A-15B illustrate the use of the syringe 1 according to the preferred embodiment of the present invention. Wherein fig. 7A, 8A, 9a … … fig. 15A shows the injection head assembly 200 and the outer structure of the syringe body 100 at various stages, while fig. 7B, 8B, 9B … … fig. 15B and 7A, 8A, 9a … … fig. 15A correspond one-to-one, with the outer housing 110 omitted in fig. 7B, 8B, 9B … … fig. 15B to clearly show the inner ram 120.

The corresponding structures of the injection head assembly 200, the syringe body 100, and the syringe 1 will be described in detail below with reference to fig. 7A to 15B, in chronological order of the usage process of the syringe 1.

Referring first to fig. 7A and 7B, the injection head assembly 200 is first mounted to the syringe body 100 prior to use. Specifically, the injection head assembly 200, when oriented at a predetermined angle relative to the syringe body 100, can be inserted in the proximal direction to a first transition position relative to the syringe body 100, at which point the proximal flange 214 of the injection head assembly 200 defining the second mating feature 212 can pass over the discontinuity of the second protrusion 111 of the syringe body 100. If the injection head assembly 200 is oriented at the wrong angle relative to the syringe body 100, the proximal flange 214 of the injection head assembly 200 defining the second mating feature 212 will be blocked by the second protrusion 111 such that the injection head assembly 200 cannot be inserted to the first transition position.

During proximal actuation of injection head assembly 200 to a first transitional position relative to syringe body 100, the circumferential ledge collectively formed by arms 232 of end cap 230 and flange 214 on injector head body 210 defining first mating feature 211 press against resilient member 112 on the distal face of outer housing 110 such that the outer surface of resilient member 112 is pressed flush with the distal face of outer housing 110. The circumferential boss is a boss that protrudes radially outward and is continuous in the circumferential direction. The proximal end of the arm 232 constitutes a first boss portion and the flange 214 constitutes a second boss portion. Since the circumferential projection is a projection that is continuous in the circumferential direction, the resilient member 112 will remain continuously compressed during subsequent rotation from the first transition position to the locked position, and will not cause resistance to rotation of the injection head assembly 200.

Preferably, when the injection head assembly 200 is in the locked position, the elastic member 112 is located at the most upstream end of the first boss portion in the mounting rotation direction R1, i.e., the elastic member 112 is located at the most upstream end of the second boss portion in the unloading rotation direction R2.

Also preferably, the front end surface of the syringe body 100 may be provided with a groove for receiving the elastic member 112 and having an axial depth smaller than the length of the elastic member 112, allowing the elastic member 112 to be removed from the groove. For example, fig. 8A, 9A, 10A, 12A, 13A, and 14A show a groove 112A for accommodating the elastic member 112. The elastic member 112 has a good elasticity and can be removed from the syringe body 100, and this arrangement can be realized: if there is indeed a loss of the end cap 230, the user may press the resilient member 112 by himself to unlock the syringe body 210; or the user may remove resilient member 112 directly from syringe body 100 to unlock syringe head body 210.

With regard to the arrangement of the circumferential projection and the elastic member, there may be some other variations than those shown and mentioned in the present embodiment. For example, the circumferential ledge defined by the end cap and the injector head body together need not be continuous in the circumferential direction, as long as the circumferential extent of the circumferential ledge is such that the resilient member is continuously compressed by the circumferential ledge during rotation of the injector head assembly from the first transition position to the second transition position. For another example, the number of arms (i.e., the number of first boss portions) and the number of flanges (i.e., the number of second boss portions) of the end cap may be three or more, the end cap may define at least two first boss portions, the injector head body may define at least two second boss portions, the first boss portions and the second boss portions may be alternately arranged in the circumferential direction, the number of elastic members may be the same as the number of first boss portions, and the elastic members and the first boss portions may be arranged in one-to-one correspondence in the circumferential position. Also, in this embodiment the first set of mating structures is provided at the spacing of the arms and flanges, but in other embodiments not shown the arms and flanges may be provided only to compress the resilient member and the engagement member between the end cap and the injector head body may be provided at other locations. The first and second boss portions may also have other arrangements than arms, flanges.

Fig. 8A and 8B illustrate the state when the injection head assembly 200 has been located at the first transitional position with respect to the syringe body 100. At this point the injection head assembly 200 cannot continue to move proximally relative to the syringe body 100, but can move distally to separate from the syringe body 100. At this time, the syringe head body 210 and the outer housing 110, and the piston rod member 220 and the inner push rod 120 are not engaged with each other. In order to contrast with the fourth protrusion 222 of the piston rod member 220, the portion at the proximal end of the piston rod member 220 other than the fourth protrusion 222 is labeled as 222 a.

Subsequently, the injection head assembly 200 is actuated in the mounting rotation direction R1 to rotate it to the second transition position shown in fig. 9A and 9B. In the second transition position, the piston rod member 220 and the inner push rod 120 are locked by the fourth set of mating structures. In particular, a radially protruding fourth protrusion 222 formed at the proximal end of the piston rod member 220 is engaged with the fourth mating feature 123 on the inner push rod 120.

Subsequently, the injector head assembly 200 is continuously actuated to rotate from the second transitional position to the locked position. During this process, piston rod assembly 220 and syringe head body 210 are disengaged, and piston rod assembly 220 remains engaged with internal ram 120, such that only syringe head body 210 and end cap 230 continue to rotate. To achieve this, a third set of mating structures between plunger rod component 220 and injector head body 210 limits relative rotation between plunger rod component 220 and injector head body 210 to less than a first predetermined torque; the fourth set of mating structures between the piston rod member 220 and the inner push rod 120 limits relative rotation between the piston rod member 220 and the inner push rod 120 at less than the second predetermined torque. The first predetermined torque is less than the second predetermined torque. When the injector head assembly 200 is rotated as a whole to the second transitional position, in which the injector head body 210 and the internal ram 120 are in locking engagement with the piston rod assembly 220, a force in the installation rotational direction R1 is applied to the injector head body 210, and when the force reaches the first predetermined torque, the injector head body 210 and the piston rod assembly 220 rotate relative to each other, and in which the relative torque between the piston rod assembly 220 and the internal ram 120 has not yet reached the second predetermined torque, so that engagement between the piston rod assembly 220 and the internal ram 120 is maintained. That is, when injector head assembly 200 is rotated to the second transition position, piston rod member 220 no longer continues to rotate.

During rotation of syringe assembly 200 from the first transitional position to the locked position, end cap 230 cannot be disengaged from syringe body 210, and the first set of mating structures between end cap 230 and syringe body 210 cannot be moved from the engaged state to the disengaged state. This is because the arms 232 of the end cap 230 need to be deformed radially outwardly to disengage the first mating features 211 on the syringe head body 210, and during rotation of the syringe head assembly 200 from the first transition position to the locked position, the arms 232 of the end cap 230 are constrained from being deformed by the outer housing 110, i.e. the outer housing 110 is radially dimensioned such that there is no room for deformation of the arms 232 of the end cap 230. When injection head assembly 200 is rotated to the locked position, there is a gap between the inner surface of outer housing 110, which is radially aligned with arm 232, and arm 232 to allow arm 232 to deform, thereby allowing end cap 230 to be removed.

The injection head assembly 200 in the locked position is shown in fig. 10A and 10B. At this point, end cap 230, rather than the syringe body, presses against the distal face of resilient member 112, so that resilient member 112 can resume deformation after end cap 230 is removed.

A drug-taking operation is required before the end cap 230 is removed. Specifically, inner ram 120 carries with it proximal actuation of plunger rod assembly 220 that the drug-extracting operation can be easily accomplished since piston rod assembly 220 has been engaged with inner ram 120 and has been disengaged from injector head body 210. Piston rod assembly 220 is moved proximally relative to syringe body 210 such that a vacuum is created within syringe body 210 and medical fluid enters syringe body 210 along a medical fluid passageway in piston rod 220a from a drug vial (not shown) housed within internal push rod 120.

After the drug is removed, and prior to the injection step, end cap 230 is removed. Fig. 11A and 11B show a schematic view of the syringe 1 with the end cap 230 removed. It should be noted again that the first set of mating structures between the end cap 230 and the injector head body 210 can be transitioned from the engaged state to the disengaged state in response to manual actuation by an operator, while the second set of mating structures are relatively firmly engaged. If the engagement of the second engagement structure group is to be released, the end cap 230 and the syringe main body 100 need to be rotated integrally in the unloading rotation direction R2. Injector head body 210 and outer housing 110 do not separate from one another under direct axial forces only, which would tend to disable the second mating feature set. Thus, when injection head assembly 200 is mounted to the locked position, the operator can actuate end cap 230 distally to remove it, an operation that does not interfere with the locking engagement between injection head body 210 and outer housing 110.

After endcap 230 is removed, elastomeric member 112, compressed by endcap 230, recovers its shape to provide resistance to rotation of syringe body 210 in unloading rotational direction R2. Thus, with end cap 230 removed, injector head body 210 cannot be rotated from the locked position back to the first transitional position. If it is desired to remove injector head body 210, end cap 230 may be reinstalled in engagement with injector head body 210.

During the injection step, the inner ram 120 is actuated, either electrically, pneumatically, or by mechanical energy provided by a spring, to move distally relative to the outer housing 110. The piston rod 220 is driven by the inner push rod 120 to compress the medical fluid in the syringe main body 210 distally, so that the medical fluid is ejected from the injection micro-holes. During drug inhalation and injection, the outer housing 110 and the injector head body 210 are stably engaged with each other through the second matching structure set; the piston rod assembly 220 and the inner push rod 120 are stably engaged by the fourth set of mating structures.

After the injection is complete, injector head assembly 200 may be removed from syringe body 100. Referring to fig. 12A and 12B, it is necessary to first proximally re-mount the end cap 230 to the syringe body 100 such that the first set of mating structures transitions from the disengaged state to the engaged state. Arm 232 of end cap 230 presses down elastic member 112, thereby releasing restriction of elastic member 112 in the rotational direction of syringe main body 210.

Subsequently, referring to fig. 13A and 13B, the injection head assembly 200 is rotated in the unloading rotation direction R2. In the process, referring to FIG. 13B, the small protrusion on the third mating feature 213 on the injector head body 210 first actuates the third protrusion 221, bringing the third protrusion 221 into disengagement with the inner ram 120. However, in other embodiments, not shown, the engagement between the piston rod member 220 and the inner ram 120 may not be affected only when the small protrusion and the third protrusion 221 are in contact, but when the syringe head body 210 continues to rotate relative to the piston rod member 220 in the unloading rotation direction R2, the stopper 218a on the third mating feature 213 and the third protrusion 221 are in contact to initiate actuation of the third protrusion 221, which then causes contact locking between the piston rod member 220 and the inner ram 120, and the piston rod member 220 can rotate with the syringe head body 210.

Fig. 14A and 14B show the injection head assembly 200 as it continues to rotate in the unloading rotational direction R2 to the first transition position. At this point, the second set of mating structures between injector head body 210 and outer housing 110 has been in a disengaged state, and the fourth set of mating structures between piston rod assembly 220 and inner ram 120 has also been in a contact engaged state. The first set of mating structures between end cap 230 and injector head body 210 are in engagement, and the third set of mating structures between injector head body 210 and piston rod assembly 220 are also in engagement. At this point injector head assembly 200 is allowed to move distally relative to outer housing 110.

Subsequently, referring to fig. 15A and 15B, the injection head assembly 200 is moved in the distal direction as a whole with respect to the syringe body 100. At this point, the syringe head assembly 200 is in an assembled state, the first set of mating structures between the end cap 230 and the syringe head body 210 are in an engaged state, and the arms 232 of the end cap 230 are located within the first mating features 211 of the syringe head body 210 defined by the flange 214; the third set of mating structures between injector head body 210 and piston rod subassembly 220 is also in an engaged state, with third protrusion 221 on piston rod subassembly 220 located within third mating feature 213 on injector head body 210.

Although in the present embodiment, when injection head assembly 200 is in the locked position, injection head body 210 is locked to outer housing 110 of syringe body 100 and piston rod assembly 220 is locked to inner ram 120 of syringe body 100. In other embodiments, however, the syringe body may include other structures, and additional mounting structures may be provided within the syringe body for engaging the syringe body and the plunger rod member, respectively. In other embodiments, the deformation of the portion of the end cap corresponding to the first set of mating structures may be limited by other components than the outer housing. In still other embodiments, the syringe body is deformed to allow the first set of mating structures to transition between the engaged state and the disengaged state, and the syringe body constrains the syringe body from deforming when the syringe assembly has been inserted into the distal end of the syringe body but has not reached the locked position. Alternatively, the injector head body and the part of the end cap corresponding to the first set of mating structures can be deformed simultaneously, thereby enabling the first set of mating structures to be transformed between an engaged state and a disengaged state, the injector body constraining the deformation of both before reaching the locked position.

The projections and the fitting features in each fitting structure group provided in the present embodiment are structures that extend in the circumferential direction and are intermittently provided. In other embodiments, not shown, the projections and mating features in each mating feature set may be structures that are arranged consecutively in the circumferential direction, and the syringe may be correspondingly adjusted in some arrangement to allow for such axially consecutive projections and mating features.

The engagement structure between the end cap and the syringe body is constrained so that the end cap and the syringe body remain engaged continuously until the injector head assembly of the present invention is properly installed in a locked position relative to the syringe body, thereby avoiding removal of the end cap in the event that the injector head body is virtually attached to the distal end of the syringe body and increasing the safety factor of operation.

In the present invention, the engagement between the piston rod member and the syringe body is also reasonable, allowing the engagement between the piston rod member and the syringe body to unlock the engagement between the piston rod member and the syringe body without manual operation by a user.

The syringe body of the present invention also has some preferred arrangements, for example, to provide a viewing window for a user to view the contents of the vial, and to allow relative axial movement between the outer housing and the inner ram while preventing relative rotation. These arrangements can both improve the accuracy and convenience of operation.

The syringe body and the injection head assembly of the present invention can be separated from each other, so that the injection head assembly or the syringe body can be conveniently replaced. Thus, the syringe body and syringe head assembly of the present invention can be manufactured and sold separately. The description and drawings relating to the injector head assembly referred to in the embodiments of the present invention should be considered to belong to the embodiments of the "injector head assembly" as well as to the embodiments of the "syringe"; the description and drawings relating to the syringe body, which are referred to in the description of the embodiments of the invention, should be considered to belong to the "syringe body" embodiment, and should also be considered to belong to the "syringe" embodiment.

In addition, although the embodiment of the present invention is exemplified by a needleless injector, the structure of the present invention can be applied to a needle injector.

From the foregoing, those skilled in the art will readily recognize alternative structures to those disclosed as possible and that combinations of the disclosed embodiments can be made to produce new embodiments, which also fall within the scope of the appended claims.

Claims

1. An injection head assembly of a syringe, the syringe (1) having a syringe body (100), the injection head assembly (200) being configured to be mountable to a distal end of the syringe body, wherein the injection head assembly comprises:

the injection head comprises an injection head main body (210), wherein a cavity (210c) with an open near end is arranged in the injection head main body, and a micropore for communicating the cavity with the outside is arranged at the far end of the injection head main body;

a piston rod component (220) having a distally extending piston rod (220a), the piston rod component being disposed proximal to the injector head body and enabling the piston rod to extend into the cavity;

an end cap (230) mounted at the distal end of the injector head body,

2. The injection head assembly of claim 1, wherein the end cap and the injection head body are engaged by a first set of mating structures that are transitionable between an engaged state such that the injection head body and the end cap are axially secured together and a disengaged state such that the injection head body and the end cap are axially separated,

3. The injector head assembly of claim 2, wherein the end cap and/or the injector head body are deformed to enable the first set of mating structures to transition between the engaged state and the disengaged state, and wherein the injector body constrains the end cap and/or the injector head body from deforming when the injector head assembly has been inserted into the distal opening of the injector body but has not reached the locked position.

4. The injector head assembly of claim 2, wherein the first set of mating structures comprises:

an arm (232) located on the end cap (230) and extending proximally from the body of the end cap, a first protrusion (233) being provided radially inward of a proximal end of the arm; and

a first mating feature (211) on the injector head body (210), a distal end of the first mating feature provided with a small step (2111),

5. The injection head assembly of claim 4, wherein the arms are deformable radially outward to axially clear the first projection from the small step,

6. The injection head assembly of claim 4, wherein the injection head assembly is configured for use with a syringe body that: the distal end face of the syringe body is provided with an elastic member (112) slightly protruding from the distal end face, and

the injector head body is provided with a circumferentially extending flange (214) which is provided intermittently and defines the first mating feature (211) at the discontinuity, the arm (232) and the flange (213) together defining a circumferentially fully extending boss configured to enable proximal compression of the resilient member (112) to bring a distal face of the resilient member and a distal face of the syringe body into alignment, and the arm (232) presses against the resilient member (112) when the injection head assembly is in the locked position.

7. The injector head assembly according to claim 2, wherein a resilient member (235) is mounted at a distal location inside the end cap, and wherein the first set of mating structures is configured to allow a small amount of axial movement between the end cap and the injector head body, such that the resilient member is compressed by the distal end of the injector head body when the injector head body and the end cap are engaged.

8. The injector head assembly of claim 1, wherein the injector head body and the syringe body are locked therebetween by a second set of mating structures that limit relative axial movement therebetween.

9. The injection head assembly of claim 8, wherein the second set of mating structures comprises:

a second protrusion (111) provided intermittently in a circumferential direction on an inner side surface of the syringe body; and

a second mating feature (212) formed on an exterior side of the injector head body, the second mating feature defined by flanges on axial sides of the second mating feature, respectively,

wherein, during mounting of the injection head assembly to the syringe body, a proximal flange (215) defining the second mating feature is axially passable through the discontinuity of the second protrusion to insert the injection head assembly into the distal opening of the syringe body, whereupon rotation of the injection head assembly relative to the syringe body causes the second protrusion to enter the second mating feature.

10. The injection head assembly of claim 1, wherein the injection head assembly is in a first transition position upon insertion into the distal opening of the syringe body, the injection head assembly being rotatable in a mounting rotational direction relative to the syringe body from the first transition position to the locked position, the injection head assembly being configured to be restricted from continuing proximal movement relative to the syringe body while in the first transition position, but to allow distal movement of the injection head assembly as a whole relative to the syringe body.

11. The injector head assembly of claim 10, wherein the injector head body is locked to an outer housing (110) of the injector body in the locked position, and there is also a second transition position between the first transition position and the locked position, the injector head assembly being configured to: in the second transition position, the piston rod member is locked to an inner ram (120) of the syringe body that is axially movable relative to the outer housing and is disengaged from the injector head body as the injector head body continues to rotate in the mounting rotation direction.

12. The injector head assembly according to claim 11, wherein the piston rod component (220) and the injector head body (210) are mated by a third set of mating features configured to limit axial relative movement and relative rotation between the piston rod component and the injector head body below a first predetermined torque,

and, a fourth set of mating structures between said piston rod member (220) and said internal push rod (120) configured to limit axial relative movement and relative rotation between said piston rod member and said internal push rod when less than a second predetermined torque,

13. The injection head assembly of claim 12, wherein the third set of mating structures comprises:

a distally extending third protrusion (221) provided on the piston rod member, a radially inner side of the third protrusion being provided with a catch;

a third mating feature (213) disposed on the injector head body, the third mating feature comprising:

a mating groove;

a catch mating portion (216) formed at a proximal end of the mating slot, the catch mating portion and catch engaging to limit proximal movement of the piston rod component relative to the injector head body;

a stopper (218a) formed on an upstream side of the fitting groove in the mounting rotational direction, the stopper blocking the third protrusion to prevent the piston rod member from rotating in the mounting rotational direction with respect to the injector head main body;

a small projection (218) formed on a downstream side of the fitting groove in the mounting rotation direction, the small projection being sized so that the third projection can pass over the small projection under an action equal to or greater than the first predetermined torque.

14. The injection head assembly of claim 12, wherein the fourth set of mating structures comprises: a radially projecting fourth boss (222) formed at the proximal end of the rod part; and a fourth mating feature (123) formed on the inner ram.

15. The injection head assembly of claim 14, wherein the piston rod component comprises:

a mounting base (224) including a radially outwardly projecting wing (224b), the piston rod extending distally from the mounting base;

a cylindrical structure (223) extending proximally from the mounting base, the fourth protrusion (222) being formed at a proximal end of the cylindrical structure.

16. The injector head assembly according to claim 12, wherein a radially inner side of the injector head body is provided with a first safety projection (219), and a radially outer side of the piston rod member is provided with a second safety projection (220c) corresponding to the first safety projection, the first and second safety projections being configured to: in the case where the plunger rod component (220) has been disengaged from the injector head body (210) but not fully engaged with the internal ram (120), the first relief projection can interfere with the second relief projection to facilitate engagement of the plunger rod component and the internal ram.

17. The injector head assembly of claim 1, wherein the injector head body comprises:

a cavity portion (210a) for receiving the piston rod of the piston rod component;

a first mating feature (211) proximal to the cavity portion and for engaging the end cap;

a second mating feature (212) proximal to the first mating feature for engagement with the syringe body;

a third mating feature (213) located proximal to the second mating feature and adapted to engage with the piston rod component.

18. The injection head assembly of claim 17, wherein the piston rod component comprises:

a piston rod mounting base;

the piston rod extending distally from the mounting base;

19. A syringe, wherein the syringe (1) comprises:

a syringe body (100) having an outer housing (110) and an inner ram (120) within and axially movable relative to the outer housing;

an injection head assembly (200) configured to be mountable to the syringe body, the injection head assembly comprising:

a piston rod component (220) having a distally extending piston rod, the piston rod component being disposed proximal to the injector head body and enabling the piston rod to extend into the cavity;

an end cap (230) disposed at a distal end of the injector head body, wherein the injector head assembly is insertable into a distal opening of the syringe body and to a locked position relative to the syringe body,

20. The syringe of claim 19, wherein the end cap and the injector head body are engaged by a first set of mating structures that are transitionable between an engaged state such that the injector head body and the end cap are axially secured together and a disengaged state such that the injector head body and the end cap are axially separated,

21. A syringe according to claim 20, wherein the end cap and/or the injector head body are deformed to enable the first set of mating structures to transition between the engaged state and the disengaged state, and wherein the syringe body constrains the end cap and/or the injector head body from deforming when the injector head assembly has been inserted into the distal opening of the syringe body but has not reached the locked position.

22. The syringe of claim 20, wherein the end cap is deformable radially outward to enable the first set of mating structures to transition between the engaged state and the disengaged state, and the injector head assembly is rotated to the locked position upon insertion into the distal opening of the syringe body,

wherein the inner diameter at the distal position of the outer housing (110) is arranged to: the inner surface of the outer housing and the outer surface of the end cap are in contact when the injection head assembly is inserted into the distal opening of the syringe body but not rotated to the locked position; when the injection head assembly is in the locked position, a radial gap exists between the inner surface of the outer housing and the outer surface of the end cap, the radial gap providing room for radial deformation of the end cap.

23. The injector of claim 20, wherein the first set of mating structures comprises:

an arm (232) located on the endcap and extending proximally from the body of the endcap, the proximal end of the arm being provided with a first protrusion (233) on an inner side thereof; and

a first mating feature (211) on the injector head body, a small step (2111) distal of the first mating feature,

24. The syringe of claim 23, wherein the arms are deformable radially outward to enable the first protrusion to clear the small step,

25. The syringe according to claim 24, wherein a distal end face of the outer housing of the syringe body is provided with an elastic member (112) slightly protruding from the distal end face, and

the injector head body is provided with a circumferentially extending flange (214) which is provided intermittently and defines the first mating feature (211) at the discontinuity, and the arm (232) and the flange together define a circumferentially fully extending boss configured to compress the resilient member proximally to bring a distal face of the resilient member and a distal face of the outer housing into alignment, and the arm presses against the resilient member when the injector head assembly is in the locked position.

26. A syringe according to claim 20, wherein a resilient member (235) is mounted at a distal end of the interior of the end cap, and the first set of mating formations are configured to allow a small amount of axial movement between the end cap and the injector head body, such that the resilient member is compressed by the distal end of the injector head body when the injector head body and the end cap are engaged.

27. The injector according to claim 19, wherein the injector head body and the injector body are locked therebetween by a second set of mating structures, the second set of mating structures comprising:

second protrusions (111) provided intermittently in a circumferential direction on an inner side surface of the outer case; and

wherein during mounting of the injection head assembly to the syringe body, the proximal flange defining the second mating feature is axially passable through the discontinuity of the second protrusion, and the injection head assembly is subsequently rotated relative to the syringe body such that the second protrusion and the second mating feature engage.

28. The injector of claim 19, wherein the injection head assembly is in a first transition position upon insertion into the distal opening of the injector body, the injection head assembly being rotatable in a mounting rotational direction relative to the injector body from the first transition position to the locked position, the injection head assembly being configured to be restricted from continuing proximal movement relative to the injector body while in the first transition position, but to allow distal movement of the injection head assembly as a whole relative to the injector body.

29. The injector according to claim 28, wherein there is also a second transition position between the first transition position and the locked position, the injection head assembly being configured to: the plunger rod component and the internal ram lock at the second transition position and disengage from the injector head body as the injector head body continues to rotate in the installation rotational direction.

30. The injector according to claim 29, wherein the piston rod component (220) and the injector head body (210) are mated therebetween by a third set of mating structures configured to limit axial relative movement and relative rotation between the piston rod component and the injector head body below a first predetermined torque,

31. The syringe of claim 30, wherein said third set of mating structures comprises:

a distally extending third protrusion (221) provided on the plunger rod member (220), a catch being provided radially inside the third protrusion;

a mating groove;

a small projection (218) formed on a downstream side of the fitting groove in the mounting rotation direction, the small projection being sized so that the third projection can pass over the small projection under the action of the torque equal to or larger than the first predetermined torque, thereby disengaging the injector head body and the piston rod member.

32. The syringe of claim 30, wherein said fourth set of mating structures comprises: a radially projecting fourth boss (222) formed at the proximal end of the rod part; and a fourth mating feature (123) formed on the inner ram.

33. The syringe of claim 30, wherein the injector head body is provided with a first safety projection (219) on a radially inner side thereof and a second safety projection (220c) corresponding to the first safety projection on a radially outer side thereof, the first and second safety projections being configured to: in the case where the plunger rod component (220) has been disengaged from the injector head body (210) but not fully engaged with the internal ram (120), the first relief projection can interfere with the second relief projection to facilitate engagement of the plunger rod component and the internal ram.

34. The syringe of claim 32, wherein the plunger rod component comprises:

a cylindrical structure (223) extending proximally from the mounting base, the fourth protrusion being formed at a proximal end of the cylindrical structure,

and, the internal thrust rod is provided with a step (1211) capable of abutting against a proximal side of the mounting base, the step being shaped to fit the wing but having a circumferential dimension slightly greater than that of the wing to allow the piston rod component to be rotatable relative to the internal thrust rod between the first and second transitional positions.

35. Syringe according to claim 34, characterized in that said step (1211) is defined by circumferential blocks (1212) at both circumferential ends thereof, able to push said wing (224b) in a direction of rotation, forcing said rod unit (220) into engagement with said internal thrust rod (120) during mounting and said rod unit (220) into engagement with said injector head body (210) during unloading.

36. The injector of claim 19, wherein the injector head body comprises:

a second mating feature (212) proximal to the first mating feature for engaging the outer housing;

37. The syringe of claim 36, wherein the plunger rod component comprises:

a piston rod mounting base;

the piston rod extending distally from the mounting base;

38. The injector according to any one of claims 19 to 37, wherein the inner ram is configured to receive a vial therein, and wherein the outer housing and the inner ram are provided with a viewing window for an operator to view the vial at a position axially aligned with the vial.

39. The injector according to claim 38, wherein the viewable window is configured to:

a plurality of hollows (124) formed on the inner push rod spaced apart in a circumferential direction, each of the hollows being formed in an elongated shape extending in an axial direction; and

a plurality of transparent parts (113) formed on the outer shell, wherein the positions of the transparent parts and the hollow parts are in one-to-one correspondence.

40. The injector according to any one of claims 19-37, wherein one of the inner surface of the outer housing and the outer surface of the inner ram is provided with an anti-rotation protrusion extending in an axial direction, and the other of the inner surface of the outer housing and the outer surface of the inner ram is provided with a keyway (125) corresponding to the anti-rotation protrusion, the anti-rotation protrusion and keyway cooperating to prevent relative rotation between the outer housing and the inner ram but allow relative axial movement between the outer housing and the inner ram.