Patent Publication Number: US-2023136095-A1

Title: Injection head of needleless syringe, needleless syringe body and needleless syringe

Description:
FIELD 
     The present disclosure relates to a medical instrument for injecting liquid medicine, and more particularly, to an injection head of a needleless syringe, needleless syringe and needleless syringe assembly. 
     BACKGROUND 
     A needleless syringe is a medical instrument which injects liquid medicine subcutaneously into a patient via a micropore at its end, without use of a needle, to relieve the pain caused by sting. The needleless syringe typically includes a medicine barrel for receiving liquid medicine, and a plunger. 
     When a needleless syringe is used, following steps are often involved: first mounting the medicine barrel onto the needleless syringe, then suctioning a medicine from the vial via the needle at the front end of the medicine barrel, and performing injection after the medicine barrel is separated from the vial. It is seen therefrom that the medicine suctioning operation is cumbersome. 
     In connection with this problem, a method has been provided in which the medicine barrel and the vial are combined as one for single use. However, such method incurs high costs, and the material for the combination of the medicine barrel and the vial cannot meet safety requirements of long-term drug contact. 
     Therefore, there arises a need for an injection head of a needleless syringe, needleless syringe body, and needleless injection assembly, to at least partly solve the above-mentioned problem. 
     SUMMARY 
     In order to cure the above deficiency, the present disclosure provides an injection head of a needleless syringe, needleless syringe body, and needleless syringe. According to the solution of the present disclosure, a vial, such as a cartridge vial and the like, can be received within a needleless syringe body, and medicine suctioning and injection can be completed efficiently and effortlessly during each use, where there is no need for removing the vial or separating the medicine barrel from the vial. Furthermore, as the vial is received within the needleless syringe body, issues such as vial loss, contamination, and the like can be prevented. 
     According to an aspect of the present disclosure, there is provided an injection head of a needleless syringe body, which is configured to be used with a vial, the injection head comprising: 
     a medicine barrel provided therein with a chamber which opens at its rear end, a front end of the medicine barrel being formed with an injection micropore communicating the chamber with the outside;
         a piston rod comprising:   a piston disposed within the chamber and configured to move within the chamber in an front-rear direction, the piston configured to define, together with a sidewall and a front wall of the medicine barrel, a medicine liquid receiving chamber;   a rod portion fixedly connected at a rear end of the piston;   wherein, in use, a rear end of the rod portion of the injection head is configured to be inserted and extend into the vial, and the piston rod is provided therein with a medicine liquid channel communicating the medicine liquid receiving chamber with the vial,
 
wherein the injection head and the vial can be mounted together to a body of the needleless syringe, and the piston rod is configured to move rearwards relative to the medicine barrel to suck medicine liquid into the medicine liquid receiving chamber via the medicine liquid channel, and move forwards relative to the medicine barrel to eject medicine liquid within the medicine liquid receiving chamber outside via the injection micropore.
       

     In an embodiment, the medicine liquid channel extends along an axis direction of the piston rod, and the piston rod at a front end is provided with a check valve only allowing the medicine liquid from the vial into the medicine liquid receiving chamber. 
     In an embodiment, the check valve comprises a valve core embedded within the piston and configured to move relative to the piston in the front-rear within a small range, and the medicine liquid from the vial flows through a gap between the valve core and the piston into the medicine liquid receiving chamber. 
     In an embodiment, the valve core is of a spherical structure; or a front portion of the valve core is of a conical structure while a rear portion is of a cylindrical structure connected to a bottom of the conical structure, a diameter of the bottom of the conical structure being greater than a diameter of the cylindrical structure. 
     In an embodiment, the piston is provided thereon with a piston inner channel extending parallel to the axis direction, an interval is provided between the piston inner channel and the piston rod in a radial direction about the axis, and the medicine fluid from the vial flows through the piston inner channel into the medicine fluid receiving chamber. 
     In an embodiment, a rear end of the rod portion is of a needle-like structure for puncturing a sealing film of the vial. 
     In an embodiment, the injection head further comprises a cap for closing the micropore removably disposed at the front end of the medicine barrel. 
     In an embodiment, the piston rod is configured to be fixed relative to the vial in use; or 
     the piston rod is configured to move rearwards relative to the vial when moving rearwards relative to the medicine barrel, to compress a medicine storage space within the vial. 
     In another aspect of the present disclosure, there is provided a needleless syringe body for use with the injection head according to any item of the above-mentioned solution and a vial, characterized in that the needleless syringe body comprises: 
     a base comprising a forward opening;
 
an outer housing comprising a rearward opening and mounted at a front end of the base to form a receiving space between the base and the outer housing, the outer housing being provided with a front opening for fixedly mounting a medicine barrel;
 
an inner push rod disposed within the receiving space and having a forward opening, the vial is fixedly received within the inner push rod, the piston rod fixed at the forward opening,
 
wherein the outer housing can move in an front-rear direction relative to the inner push rod to drive the medicine barrel to move in an front-rear direction relative to the vial and the piston rod, so as to implement medicine suctioning and injection.
 
     In an embodiment, the needleless syringe body further comprises a locking mechanism connected between the base and the inner push rod, and the locking mechanism is configured to lock the inner push rod relative to the base in a medicine suctioning process, and unlock the inner push after medicine suction to cause the inner push rod to move forwards relative to the outer housing. 
     In an embodiment, the inner push rod at a rear end is provided with a rear end flange protruding radially outwards, and the locking mechanism comprises: 
     a limiting member configured to abut against a front end face of the rear end flange in a locked state to limit forward movement of the inner push rod;
 
a button mounted on a rear end wall of the base and protruding rearwards relative to the base,
 
wherein the button is configured to be pushed to move forward relative to the base and apply directly or indirectly a thrust to a rear end face of the inner push rod, and the rear end flange of the inner push rod can pass over the limiting member as an effect of the thrust, causing the locking mechanism to unlock the inner push rod.
 
     In an embodiment, the locking mechanism further comprises: 
     a spring receiving member disposed between a rear end face of the inner push rod and a rear end wall of the button and having a spring receiving chamber opening rearwards;
 
a button spring disposed in the spring receiving chamber and configured to contact at its rear end with the button;
 
wherein the button can be pushed to indirectly apply a thrust to the inner push rod via the button spring and the spring receiving member.
 
     In an embodiment, the button has a rear end wall, and a sidewall extending forwards from the rear end wall and surrounding the axis, the sidewall at a front end is provided with a protrusion portion protruding towards an axis of the needleless syringe body, and the limiting member is configured to move relative to the button in a radial direction relative to the axis, 
     wherein, in a locked state, the protrusion portion abuts against a radial outside of the limiting member to limit radial outward movement thereof, the protrusion portion moves forwards relative to the limiting member when the button is pushed, to release radial restrictions thereon, and at this time, the limiting member can move radially outwards to disengage from the front end face of the rear end flange, thereby unlocking the inner push rod. 
     In an embodiment, the limiting member is a sphere, and a rear end face of the protrusion portion and a front end face of the rear end flange are slopes, such that the limiting member can be in rolling contact with the slopes during unlocking. 
     In an embodiment, the locking mechanism is an electromagnet. 
     In an embodiment, the needleless syringe body further comprises a resilient actuation mechanism disposed between the base and the inner push rod, which is configured to be operated before injection for energy accumulation, and to be released after energy accumulation to actuate the inner push rod forwards via a resilient force to complete injection. 
     In an embodiment, the inner push rod at an inner end is provided with a front end flange protruding radially outwards, and the resilient actuation mechanism comprises an actuation spring disposed between the front end flange and the base. 
     In an embodiment, the actuation spring is sleeved outside the inner push rod. 
     In an embodiment, a spring shaft  37  is fixedly connected on a front end flange of the inner push rod, which is parallel to an axis of the inner push rod and onto which the actuation spring is sleeved. 
     In an embodiment, a plurality of the spring shafts are provided, each being sleeved thereon with the actuation spring, the spring shafts being arranged around the inner push rod. 
     In an embodiment, the inner push rod in the middle is provided with a middle flange disposed along its peripheral direction, and the spring actuation mechanism comprises an actuation spring between the middle flange and the base. 
     In an embodiment, the base comprises a rear end portion and a base sidewall, the base sidewall at an inner surface is provided with internal threads, the outer housing at a rear outer surface is provided with external threads corresponding to the internal threads, and cooperation of the internal threads and the external threads enables the outer housing to move rearwards relative to the base, thereby stably compressing the actuation spring. 
     In an embodiment, respective portions of the outer housing and the inner push rod facing the vial in a radial direction are configured to be at least partly transparent or hollow, making a volume of medicine liquid within the vial visible. 
     According to a further aspect of the present disclosure, there is provided a needleless syringe, comprising the needleless syringe body according to any item of the above-mentioned solution and an injection head for use with the needleless syringe body. 
     In an embodiment, an outer housing of the needleless syringe body at a front opening is provided with internal threads facing an axis of the needleless syringe, a medicine barrel of the injection head is provided with external threads, and with cooperation of the internal threads and the external threads, the medicine barrel can be removably mounted on the needleless syringe body. 
     According to a still further aspect, there is provided a needleless syringe body for use with an injection head and a vial, the vial comprising a vial body having a vial receiving chamber, and a cork slidable within the vial receiving chamber in an front-rear direction relative to the vial body, characterized in that the needleless syringe body comprises: 
     a base having a forward opening;
 
an outer housing having a rearward opening and mounted at a front end of the base to form a receiving space between the base and the outer housing, the outer housing provided with a front opening for fixedly mounting a medicine barrel;
 
an inner push rod system comprising an inner push rod disposed within the receiving space and having a forward opening, the vial is fixedly received within the inner push rod, the piston rod is fixed at the forward opening;
 
a medicine supply push rod mounted at a rear end of the inner push rod, the medicine supply push rod at a front end being in contact with the cork of the vial; and
 
transmission means, wherein a part of the transmission means is connected to the medicine supply push rod while the other part thereof is directly or indirectly connected to the base or the outer housing,
 
wherein the outer housing can move in an front-rear direction relative to the inner push rod, to drive the medicine barrel to move in the front-rear direction relative to the vial and the piston rod, to implement medicine suctioning and injection, and
 
wherein, in a medicine suctioning process, the base or the outer housing drives, via the transmission means, the medicine supply push rod to move the cork of the vial forwards relative to the vial body, so as to compress a space within the vial.
 
     In an embodiment, the needleless syringe body further comprises a locking mechanism connected between the base and the inner push rod system, which is configured to lock the inner push rod system in a medicine suctioning process to lock the inner push rod system in an front-rear direction relative to the base, and to unlock the inner push rod system after medicine suctioning to move forwards relative to the outer housing. 
     In an embodiment, the base and the outer housing are engaged and being rotatable relative to each other, such that, through relative rotation between the outer housing and the base, relative movement of the two can be achieved in an axis direction of the needleless syringe body. 
     In an embodiment, the inner push rod system further comprises a transmission rod which is connected at a front end to the transmission means and engaged at a rear end with the locking mechanism, and the transmission rod is fixed relative to the base in a rotational direction relative to the base when locked by the locking mechanism. 
     In an embodiment, the transmission means comprises transmission means for rotational movement which is configured to transmit specified rotational movement of the transmission rod to the medicine supply push rod to drive the medicine supply push rod to rotate; and 
     the needleless syringe body is provided therein with a movement conversion mechanism, and a part of the movement conversion mechanism is engaged with the medicine supply push rod while the other part of the movement conversion mechanism is directly or indirectly engaged with the inner push rod to convert rotational movement of the medicine supply push rod along with the transmission rod into linear movement of the inner push rod. 
     In an embodiment, in the medicine suctioning process, the outer housing rotates relative to the base to move forwards relative to the same; and 
     the transmission means for rotational movement comprises one-way transmission means for rotational movement which is configured to transmit the rotational movement of the transmission rod to the medicine supply push rod when the outer housing rotates relative to the base to move forwards relative to the base, and not to transmit the rotational movement of the transmission rod to the medicine supply push rod when the outer housing rotates relative to the base to move rearwards relative to the same. 
     In an embodiment, the one-way transmission means for rotational movement comprises a one-way bearing, which is fixedly connected at an outer ring to the transmission rod, and fixedly connected at an inner ring to the medicine supply push rod in a rotational direction about the axis of the needleless syringe body. 
     In an embodiment, the movement conversion mechanism comprises a nut member received in a receiving space of the inner push rod and fixedly connected to the inner push rod, and the medicine supply push rod is engaged with the nut member in thread fit. 
     In an embodiment, the nut member comprises at least two nut members separated from each other, which are arranged around the medicine supply push rod and can move towards or away from the axis of the needleless syringe body in a radial direction of the needleless syringe body, so as to engage with or disengage from the medicine supply push rod. 
     In an embodiment, the at least two nut members are configured to move radially in a direction away from the axis and thus disengage from the medicine supply push rod, when the medicine supply push rod applies a force in an axial direction of the needleless syringe body to the nut members and the force reaches a predetermined threshold. 
     In an embodiment, a resilient member is mounted between circumferential outer surfaces of the nut members and a circumferential inner surface of the inner push rod, which is compressed when the two nut members disengage from the medicine supply push rod. 
     In an embodiment, the needleless syringe body further comprises a nut limiting member at a front end of each of the nut members, wherein a surface of the nut member contacting with the nut limiting member is a force bearing slope, a rear end of the force bearing slope is radially farther away from the axis of the needleless syringe than a front end thereof, and the nut limiting member is configured to urge the force bearing slope rearwards to press the nut member into engagement with the medicine supply push rod, and to cause, when stopping applying the force to the nut member, the nut member to move radially away from the other and thus disengage from the medicine supply push rod. 
     In an embodiment, the front end of the nut limiting member can be in direct contact with a rear end of the vial body, to press the nut member continuously as an effect of a rearward force of the vial body when the vial is mounted within the inner push rod, and the nut limiting member stops applying the force to the nut limiting member after the vial is removed from the inner push rod. 
     In an embodiment, the nut limiting member is a wedge which has a force applying slope contacting with the force bearing slope. 
     In an embodiment, the nut limiting member is of a spherical structure, and a sphere movement slot is provided at a front end of a radial outer edge of the nut member, within which the nut limiting member is limited, making it impossible to escape therefrom. 
     In an embodiment, the nut limiting member is of an annular structure coaxial with the needleless syringe body, and a section of the annular structure after cut by a plane where its axis is located is circular. 
     In an embodiment, the inner push rod system at a rear end is provided with a rear end flange protruding radially outwards, and the locking mechanism comprises: 
     a limiting member configured to abut in a locked state against a front end face of the rear end flange to limit forward movement of the inner push rod system;
 
a button mounted at a rear end wall of the base and protruding rearwards from the base,
 
wherein the button is configured to be pushed to move forwards relative to the base and to directly or indirectly apply a thrust to a rear end face of the inner push rod system, and the rear end flange of the inner push rod system can pass over the limiting member as an effect of the thrust, thereby causing the locking mechanism to unlock the inner push rod system.
 
     In an embodiment, the locking mechanism further comprises: 
     a spring receiving member disposed between a rear end face of the inner push rod system and a rear end wall of the button and having a spring receiving chamber opening rearwards;
 
a button spring disposed within the spring receiving chamber and configured at its rear end to contact with button,
 
wherein the button can be pushed to indirectly apply a thrust to the inner push rod system via the button spring and the spring receiving member.
 
     In an embodiment, the button has a rear end wall and a sidewall extending forwards from the rear end wall and around the axis, the side wall at a front end is provided with a protrusion portion protruding towards an axis of the needleless syringe body, and the limiting member is configured to move relative to the button in a radial direction relative to the axis, 
     wherein, in a locked state, the protrusion portion abuts against a radial outside of the limiting member to limit radial outward movement thereof, the protrusion portion moves forwards relative to the limiting member when the button is pushed, to release radial restrictions thereon, and at this time, the limiting member can move radially outwards to disengage from a front end face of the rear end flange, thereby unlocking the inner push rod system. 
     In an embodiment, the limiting member is a sphere, and a rear end face of the protrusion portion and a front end face of the rear end flange are both slopes such that the limiting member can be in rolling contact with the slopes in the unlocking process. 
     In an embodiment, the locking mechanism is an electromagnet. 
     In an embodiment, the needleless syringe body further comprises a resilient actuation mechanism disposed between the base and the inner push rod system, which is configured to be operated for energy accumulation prior to injection, and to be released after energy accumulation to actuate the inner push rod system forwards, so as to complete injection. 
     In an embodiment, the inner push rod at a front end is provided with a front end flange protruding radially outwards, and the resilient actuation mechanism comprises an actuation spring disposed between the front end flange and the base. 
     In an embodiment, the actuation spring is sleeved outside the inner push rod. 
     In an embodiment, a spring shaft is fixedly connected at the front end flange of the inner push rod, which is parallel to an axis of the inner push rod and onto which the actuation spring is sleeved. 
     In an embodiment, a plurality of the spring shafts are provided, each being sleeved thereon with the actuation spring, the spring shafts being arranged around the inner push rod. 
     In an embodiment, the inner push rod in the middle is provided with a middle flange disposed along its peripheral direction, and the spring actuation mechanism comprises an actuation spring between the middle flange and the base. 
     In an embodiment, the base comprises a rear end portion and a base sidewall, the base sidewall at an inner surface is provided with internal threads, the outer housing at a rear outer surface is provided with external threads corresponding to the internal threads, and cooperation of the internal threads and the external threads enables the outer housing to move rearwards relative to the base, thereby stably compressing the actuation spring. 
     In an embodiment, respective portions of the outer housing and the inner push rod facing the vial in a radial direction are configured to be at least partly transparent or hollow, making a volume of medicine liquid within the vial visible. 
     In an embodiment, the inner push rod at an outer periphery is provided with an inner push rod flange protruding radially outwards, a circumferential outer surface of the inner push rod flange is in contact with a circumferential inner surface of the outer housing, and the circumferential outer surface of the inner push rod flange and the circumferential inner surface of the outer housing are provided with a movement limiting feature which is configured to limit rotation of the inner push rod relative to the outer housing while permitting the inner push rod to move in an front-rear direction relative to the outer housing. 
     In an embodiment, the movement limiting feature comprises a keyway or guide rod formed on the circumferential outer surface of the inner push rod flange and the circumferential inner surface of the inner housing and extending along an axis direction of the needleless syringe body. 
     According to a still another aspect of the present disclosure, there is provided a needleless syringe, comprising the needleless syringe body according to any item of the solution and an injection head for use with the needleless syringe body. 
     In an embodiment, the injection head can be used with a vial, the injection head comprising: 
     a medicine barrel provided therein with a chamber which opens at its rear end, a front end of the medicine barrel being formed with an injection micropore communicating the chamber with the outside;
 
a piston rod comprising:
         a piston disposed within the chamber and configured to move within the chamber in an front-rear direction, the piston configured to define, together with a sidewall and a front wall of the medicine barrel, a medicine liquid receiving chamber;   a rod portion fixedly connected at a rear end of the piston;   wherein, in use, a rear end of the rod portion of the injection head is configured to be inserted and extend into the vial, and the piston rod is provided therein with a medicine liquid channel communicating the medicine liquid receiving chamber with the vial,
 
wherein the injection head and the vial can be mounted together on a body of the needleless syringe, and the piston rod is configured to move rearwards relative to the medicine barrel to suck medicine liquid into the medicine liquid receiving chamber via the medicine liquid channel, and move forwards relative to the medicine barrel to eject medicine liquid within the medicine liquid receiving chamber outside via the injection micropore.
       

     In an embodiment, the medicine liquid channel extends along an axis direction of the piston rod, and the piston rod at a front end is provided with a check valve only allowing the medicine liquid from the vial into the medicine liquid receiving chamber. 
     In an embodiment, the check valve comprises a valve core embedded within the piston and configured to move relative to the piston in the front-rear within a small range, and the medicine liquid from the vial flows through a gap between the valve core and the piston into the medicine liquid receiving chamber. 
     In an embodiment, the valve core is of a spherical structure; or a front portion of the valve core is of a conical structure while a rear portion is of a cylindrical structure connected to a bottom of the conical structure, a diameter of the bottom of the conical structure being greater than a diameter of the cylindrical structure. 
     In an embodiment, the piston is provided with thereon with a piston inner channel extending parallel to the axis direction, an interval is provided between the piston inner channel and the piston rod in a radial direction about the axis, and the medicine fluid from the vial flows through the piston inner channel into the medicine fluid receiving chamber. 
     In an embodiment, a rear end of the rod portion is of a needle-like structure for puncturing a sealing film of the vial. 
     In an embodiment, the injection head further comprises a cap for closing the micropore removably disposed at the front end of the medicine barrel. 
     In an embodiment, internal threads facing an axis of the needleless syringe are disposed at a front opening of an outer housing of the needleless syringe body, external threads are provided on the medicine barrel of the injection head, and cooperation of the internal threads and the external threads enables removable mounting of the medicine barrel on the needleless syringe body. 
     According to the present disclosure, a vial, such as a cartridge vial and the like, can be received within a needleless syringe body, and medicine suctioning and injection can be completed efficiently and effortlessly during each use, where there is no need for removing the vial or separating the medicine barrel from the vial. Furthermore, as the vial is received within the needleless syringe body, issues such as vial loss, contamination, and the like can be prevented. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For the sake of better understanding on the above and other objectives, features, advantages, and functions of the present disclosure, preferred embodiments are provided with reference to the drawings. The same or similar reference symbols refer to the same or similar components throughout the drawings. It would be appreciated by those skilled in the art that the drawings are merely provided to illustrate preferred embodiments of the present disclosure, without suggesting any limitation to the protection scope of the present disclosure, and respective components therein are not necessarily drawn to scale. 
         FIG.  1    is a section view of an injection head of a needleless syringe according to a preferred embodiment of the present disclosure in a explosive state; 
         FIG.  2    is a section view of the injection head in  FIG.  1    in a state connected to a vial; 
         FIG.  3    is a section view of the injection head in  FIG.  2    during a medicine suctioning process; 
         FIG.  4    is a section view of the injection head in  FIG.  2    during an injection process; 
         FIGS.  5  and  6    are section views of a front end of the injection head in  FIG.  2    at a prepared state and a medicine suctioning state, respectively; 
         FIGS.  7 - 8    are section views of an alternative solution of the in  FIGS.  5 - 6   ; 
         FIGS.  9 - 10    are section views of a further alternative solution of the in  FIGS.  5 - 6   ; 
         FIG.  11    is a section view of a needleless syringe body according to a preferred embodiment of the present disclosure; 
         FIG.  12    is a section view of a rear end of the needleless syringe in  FIG.  11   , where a locking mechanism is in a locked state; 
         FIG.  13    is a further section view of the rear end of the needleless syringe in  FIG.  11   , where the locking mechanism is in a unlocked state; 
         FIGS.  14 - 19    are section views of the needleless syringe when the injection head and the vial are mounted to a needleless syringe body, and the needleless syringe is used in a medicine suctioning process and a needleless-injection process; 
         FIG.  20    is a section view of an alternative solution of the needleless syringe in  FIGS.  14 - 19   ; 
         FIG.  21    is a section view of a further alternative solution of the needleless syringe in  FIGS.  14 - 19   ; 
         FIGS.  22 - 28    are section views of a needleless syringe when an injection head and a vial are mounted to a needleless syringe body, and the needleless syringe is used in a medicine suctioning process and a needleless-injection process, according to a further preferred embodiment; 
         FIG.  29    is a section view of the needleless syringe body in  FIGS.  22 - 28    after finishing needleless injection; 
         FIG.  30 A  is a section view of the structure in  FIGS.  22 - 28    where an inner push rod system, a nut member and a one-way bearing are in an assembled state; 
         FIG.  30 B  is a schematic diagram cut along an A-A axis from  FIG.  30 A ; 
         FIG.  31    is a section view of the structure in  FIGS.  22 - 28    where an inner push rod system, a nut member and a one-way bearing are in an assembled state, according to an alternative embodiment; 
         FIG.  32 A  is a schematic diagram of respective members in  FIG.  31    when the nut member and a medicine supply push rod are in an engaged state; 
         FIG.  32 B  is a schematic diagram of respective members in  FIG.  31    when the nut member and the medicine supply push rod are in a disengaged stated; 
         FIGS.  33 A- 33 B  are schematic diagrams of an alternative solution of  FIGS.  32 A- 32 B ; and 
         FIGS.  34 A- 34 B  are schematic diagrams of a further alternative solution of  FIGS.  32 A- 32 B . 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     Reference now will be made to the drawings to describe a needleless syringe, needleless syringe body, and injection head of the needleless syringe. What will be described herein are only preferred embodiments according to the present disclosure. On the basis of the preferred embodiments, those skilled in the art would envision other embodiments which also fall into the scope of the present disclosure. 
     The present disclosure provides an injection head of a needleless syringe, a needleless syringe body and the needleless syringe.  FIGS.  1 - 34 B  illustrate some preferred embodiments according to the present disclosure. 
     It is worth noting that the “axial direction” here is to be read as a direction of an axis X of the needleless syringe; in the axis direction, a direction facing a patient during use of the needleless syringe is referred to as “front side”, while the opposite direction is referred to as “rear side”. The “radial direction” here is to be read as radial direction about the axis direction, which is denoted by X′ in  FIG.  15   . 
       FIG.  1    is a schematic diagram of an injection head  2  of a needleless syringe according to a preferred embodiment in a explosive state. The injection head  2  is used with a vial  1  which may be a cartridge vial in line with the national standards, for example.  FIGS.  2 - 4    are schematic diagrams illustrating a connection between the injection head  2  and the vial  1 , in which the injection head  2  and the vial  1 , if connected correctly, can be mounted jointly on the needleless syringe body  3  (see  FIG.  11   ). 
     As can be seen from  FIGS.  1 - 4   , the injection head  2  is substantially a rotational symmetric structure about an axis X, and specifically includes a medicine barrel  21  and a piston rod  22 . The medicine barrel  21  is provided therein with a chamber that opens at the rear end. An injection micropore  211  communicating the chamber with the outside is formed at the front end of the medicine barrel  21 . The piston rod  22  includes a piston  221  and a rod portion  222 , where the piston  221  is disposed within the chamber and movable within the chamber in an front-rear direction, the piston  221  and the sidewall and front wall of the medicine barrel  21  can jointly define a medicine liquid receiving chamber  215 , and the rod portion  222  is fixedly connected at the rear end of the piston  221  and extends into the vial  1 . Moreover, the piston rod  22  is provided therein with a liquid medicine channel  222   c  for communicating the medicine liquid receiving chamber  215  with the vial  1 . The liquid medicine channel  222   c  preferably extends along the axis X. 
     Preferably, the rear end of the rod portion  222  is of a needle-like structure  222   b  for puncturing a sealing film at the front end of the vial  1 . Similarly preferably, the injection head  2  may further include a cap  23  removably disposed at the front end of the vial  221  for closing the injection micropore  211 . The cap  23  may be provided thereon with a cap protrusion  231 , the medicine barrel may be provided thereon with a medicine barrel recess  214 , and the cap protrusion  231  and the medicine barrel recess  214  can engage with each other to enable convenient mounting of the cap  23  on the medicine barrel  21 . In other embodiments not shown, a cap  23  may not be provided additionally, and the medicine barrel  21  is configured to cause the injection micropore  211  to be self-opened and self-closed. 
     Referring to  FIG.  3   , when the cap  23  is mounted at the front end of the medicine barrel  21 , the piston rod  22  moves rearwards relative to the medicine barrel  21 . At this time, negative pressure is formed within the medicine liquid receiving chamber  215  to suction the medicine liquid within the vial  1  via the medicine liquid channel  222   c  into the medicine liquid receiving chamber  215 . Preferably, a rear end of a medicine storage space of the vial  1  may be closed by a movable cork  12  which is configured to move freely relative to the vial body  11  under the gas pressure. In other words, during the medicine suctioning process, the cork  12  can move forwards relative to the vial body  11  to ensure that the pressure within the medicine storage space is not reduced to keep the medicine suctioning rate at a stable level throughout the whole process. Referring to  FIG.  4   , after completion of medicine suction, the cap  23  may be removed, and the piston rod  22  is controlled to move forwards relative to the medicine barrel  21 , so as to eject the medicine liquid within the medicine liquid receiving chamber  215  via the injection micropore  211 . 
     In order to prevent the medicine fluid from flowing back from the medicine fluid receiving chamber  215  into the vial  1  and thus cause contamination, the piston rod  22  at the front end may be provided with a check valve which is configured to only allow the medicine liquid to flow from the vial  1  into the medicine liquid receiving chamber  215 .  FIGS.  5  to  10    illustrate three embodiments of the check valve. 
     Two types of check valves as shown in  FIGS.  5 - 8    include a valve core embedded in the piston  221 , and the valve core is movable in a small range relative to the piston  221  in an anterior-posterior direction. The valve core is formed in a rotatable symmetric structure relative to the axis. The medicine liquid from the vial  1  should flow through a gap between the valve core and the piston  221  into the medicine liquid receiving chamber  215 . In other embodiments not shown, the valve core may be of an asymmetric structure. Specifically, in this embodiment, due to the negative pressure in the medicine suctioning process, the piston  221  is deformed, and the valve core is moved slightly forwards relative to the piston  221  under the suctioning force, such that a path can be formed between the valve core and the piston  221 . Upon completion of the medicine suctioning, movement of the piston rod  22  is stopped. At this time, the medicine liquid is supplied via the path into the medicine liquid receiving chamber, and the negative pressure disappears. In particular, after the cap  23  is removed from the medicine barrel  21 , the pressure within the medicine liquid receiving chamber is identical to the external pressure due to the micropore  211  at the front end of the medicine barrel  21 . By this time, the valve core is forced back to the original site to prevent backflow of the medicine liquid. 
     Specifically, the check valve according to an embodiment as shown in  FIGS.  5  and  6    is a ball valve, where the valve core  223  is spherical, and the piston  221  is provided with a receiving structure adapted to the outer contour of the sphere.  FIG.  5    is schematic diagram when no medicine liquid flows through the valve core  223 , and  FIG.  6    is a schematic diagram when a medicine liquid flows through the valve core  223 . As shown in  FIG.  6   , the medicine liquid reaches the valve core  223  via the medicine liquid channel  222   c  and then flows through the gap between the valve core  223  and the piston  221  (i.e., bypassing the valve core  223 ) into the medicine liquid receiving chamber  215 . 
     A valve core  224  of a check valve according to a further embodiment as shown in  FIGS.  7  and  8    includes two portions, namely a front portion which is a conical structure  224   a  and a rear portion which is a cylindrical structure  224   b , where the cylindrical structure  224   b  is connected to the bottom of the conical structure  224   a , and the diameter of the bottom of the conical structure  224   a  is greater than the diameter of the cylindrical structure  224   b . Preferably, the front end face  221   b  of the piston  221 ′ matches the rear end face of the conical structure  224   a , and when the valve core  224  is mounted on the piston  221 ′, the front end of the whole structure of the valve core  224  and the piston  221 ′ happens to form a conical structure. The valve core  224  is formed of a resilient material. During the medicine suctioning process, due to the negative pressure within the medicine liquid receiving chamber (there additionally exists the impact of the medicine liquid), the front end of the conical structure  224  is subjected to a forward suction force. On the other hand, the cylindrical portion  224   b  at the rear end is provided with a small protrusion  224   c  engaging with the piston  221 ′, and since the front end of the valve core  224  is subjected to a forward suction force while the rear end is fixed relative to the piston  221 ′, the valve core  224  is slightly deformed, causing the conical portion  224   a  of the valve core  224  to move slightly forwards relative to the piston  221 ′, such that a gap is formed between the conical portion  224   a  of the valve core  224  and the piston  221 ′ through which the medicine liquid can flow into the medicine liquid receiving chamber  215 . 
       FIGS.  9  and  10    illustrate a check valve structure according to a further embodiment. The check valve in  FIGS.  9  and  10    is not provided with a valve core, but the piston  211 ″ is provided therein with a piston inner channel  221   c  which may be parallel to the axial direction, or angled relative to the axial direction. The piston inner channel  221   c  and the piston rod  22  are spaced apart in the radial direction about the axis. The medicine liquid from the vial  1  flows sequentially through the medicine liquid channel  222   c  within the rod portion  222  and the piston inner channel  221   c  within the piston  221 ″ into the medicine liquid receiving chamber  215 . 
     In the embodiment as shown, the piston rod  22  is fixed relative to the vial  1  during medicine suctioning and injection operations, and the medicine liquid is introduced from the vial  1  into the medicine liquid receiving chamber  214  in the medicine suctioning process, only as an effect of a difference between pressures within the medicine liquid receiving chamber  215  and the vial  1 . However, in other embodiments not shown, the piston rod  22  at the rear end may be provided with a piston movable within the vial. During the medicine suctioning process, the piston rod  22  moves rearwards relative to both the medicine barrel  21  and the vial  1 , thereby compressing the space within the vial by a piston within the vial. Such operation can further increase the medicine suctioning rate. 
       FIG.  11    illustrates a preferred embodiment of a needleless syringe body  3 , which is used together with the injection head  2  and the vial  1  as described above. As shown in  FIG.  11   , the needleless syringe body  3  includes a base  31 , an outer housing  32  and an inner push rod  33 . The base  31  includes a forward opening. The outer housing  32  is provided with a rearward opening and mounted at the front end of the base  31  such that a receiving space is formed between the base  31  and the outer housing  32 . The outer housing  32  is further provided with a front opening for fixedly mounting the medicine barrel  21 . The inner push rod  33  is disposed within the receiving space and is provided a forward opening. The vial  1  can be received within the inner push rod  33  and moves along with the inner push rod  33 . The piston rod  22  is fixedly mounted at the forward opening. 
     The connecting way of the components as mentioned above may be of multiple types. For example, a threaded connection may be provided between the outer housing  32  and the medicine barrel  21 . Referring to  FIG.  14   , the outer surface of the rear portion of the medicine barrel  21  is provided thereon with medicine-barrel external threads  213 , the front opening of the outer housing  32  is provided with in-housing internal threads  322   a , and the medicine-barrel external threads  213  can cooperate with the in-housing internal threads  322   a  to secure the medicine barrel  21  and the outer housing  32  relative to each other. The medicine barrel  21  may be provided with a limiting flange  212  for engagement on the front end face of the outer housing  32 . 
     The piston rod  22  may be cooperated with the inner push rod  33  in snap fit. Specifically, continuing with  FIG.  14   , the piston rod  22  at the outer surface is provided with a snap-fit protrusion  222   d , the inner push rod  33  at the corresponding position is provided with a snap-fit recess  33   a , and the snap-fit protrusion  222   d  is snap-fitted into the snap-fit recess  33   a  to secure the piston rod  22  relative to the inner push rod  33 . The rear portion  222   a  of the piston rod  22  may be of a large radial size to match the inner push rod  33 . Further, the space within the inner push rod  33  may be of a size adapted to the vial  1 , and after the piston rod  22  is snap-fitted with the inner push rod  33 , the vial  1  is adaptively disposed in the space which leaves no room for movement of the vial  1  relative to the inner push rod  33 . 
     As such, throughout the medicine suctioning and injection process, the outer housing  32  is fixed relative to the medicine barrel  21 , the inner push rod  33  is fixed relative to both of the vial  1  and the piston rod  22 , but the outer housing  32 , the inner push rod  33  and the base  31  are movable relative to one other. Therefore, the outer housing  32  can drive the medicine barrel  21  to move, and the inner push rod  33  can drive the vial  1  and the piston  221  to move. 
     Specifically, the outer housing  32  can move in an front-rear direction relative to the inner push rod  33  to drive the medicine barrel  21  to move in an front-rear direction relative to the vial  1  and the piston  22 , thereby implementing medicine suction and injection. More specifically, during the medicine suctioning process (see  FIG.  17   ), the inner push rod  33  is fixed relative to the base  31 , and the outer housing  32  moves forwards relative to the inner push rod  33 ; during the injection process (see  FIG.  19   ), the outer housing  32  is fixed relative to the base  31 , and the inner push rod  33  moves forwards relative to outside inner push rod  33  outer housing  32 . The specific medicine suction and injection process will be described below in detail. 
     Preferably, the needleless syringe body  3  further includes a locking mechanism  34  which is connected between the base  31  and the inner push rod  33  to lock the inner push rod  33  relative to the base  31  during the medicine suctioning process, and to unlock the same after medicine suction to cause the inner push rod  33  to move forwards relative to the outer housing  32 . 
       FIGS.  12  and  13    illustrate a preferred embodiment of the locking mechanism  34 , in which the inner push rod  33  is not shown.  FIG.  12    shows a locked state of the locking mechanism  34  while  FIG.  13    shows an unlocked state.  FIGS.  16 - 19    illustrate a state where the inner push rod  33  is mated with the locking mechanism  34 . 
     The rear end of the inner push rod  33  is provided with a rear end flange  333  protruding radially outwards (see  FIG.  16   ) for mating with the locking mechanism  34 . Referring to  FIGS.  12 ,  13  and  16   , the locking mechanism  34  includes a limiting member  344 , button  341 , spring receiving member  342  and button spring  343 . The limiting member  344  in the locked state can abut against a front end face  333   a  of the rear end flange  333  to limit forward movement of the inner push rod  33 ; the button  341  is mounted at the rear end wall of the base  31  and protrudes rearwards relative to the base  31 ; the spring receiving member  342  is provided between the rear end face of the inner push rod  33  and the rear end wall of the button  341 , which has a spring receiving chamber that opens rearwards; and the button spring  343  is disposed within the spring receiving chamber and can contact at its rear end with the button  341 . 
     In this way, the button  341  can be pushed, and the button spring  343  and the spring receiving member  342  in turn are pushed to indirectly push the inner push rod  33  such that the rear end flange  333  of the inner push rod  33  can pass over the limiting member  344 , causing the locking mechanism  34  to unlock the inner push rod  33 . In other embodiments not shown, such members as the spring button  343 , the spring receiving member  342 , and the like may not be provided, and the button  341  directly pushes the inner push rod  33 , causing the locking mechanism  34  to unlock the inner push rod  33 . 
     Preferably, continuing with  FIGS.  12 - 19   , the button  341  includes a rear end wall and a sidewall  341   b  extending around the axis X and forwards from the rear end wall, the sidewall  341   b  at the front end is provided with a protrusion portion  341   c  protruding towards the axis of the needleless syringe body  3 , and the limiting member  344  is movable relative to the button  341  in a radial direction about the axis. Wherein, in the locked state as shown in  FIGS.  12  and  16 - 18   , the protrusion portion  341   c  abuts against the radial outside of the limiting member  344  to limit its radial outward movement. As being unable to move radially outwards, the limiting member  344  can stably abut against the front end face  333   a  of the rear end flange  333  of the inner push rod  33  to lock the inner push rod  33 ; when the button  341  is pushed, the protrusion portion  341   c  moves forwards relative to the limiting member  344  to release its radial limit, and the limiting member  344  thus can move radially outwards to disengage from the front end face of the rear end flange  333  of the inner push rod  33 , thereby unlocking the inner push rod  33 .  FIGS.  13  and  19    show the state after unlocking the locking mechanism  34 . 
     More preferably, the limiting member  344  may be two spheres disposed symmetrically about the axis. The rear end face  34   d  (see  FIG.  12   ) of the protrusion portion  341   c  and the front end face  333   a  (see  FIG.  11   ) of the rear end flange  333  of the inner push rod  33  are both slopes, and the limiting member  344  can be in rolling contact with the slopes during the unlocking process, such that a user can achieve unlocking only upon application of a small thrust onto the button  341 . 
     In other embodiments not shown, other locking mechanism  34  may also be provided. For example, the locking mechanism  34  may be an electromagnet. After the injection head  2  and the vial  1  are mounted within the needleless syringe body  3 , the electromagnet may be powered on to lock the inner push rod  33  and then medicine suction is performed. After medicine suction is completed, the electromagnet may be powered off, thereby losing magnetism. At this time, the inner push rod  33  can move forwards relative to the outer housing  32  to implement injection. 
     Preferably, referring to  FIGS.  11  and  14 - 19   , the needleless syringe body  3  further includes a resilient actuation mechanism located between the base  31  and the inner push rod  33 . The resilient actuation mechanism is configured to be operated before injection for energy accumulation and then release the energy to actuate the inner push rod  33  forwards through a resilient force, and the inner push rod  33  then drives the piston rod  22  to compress the medicine liquid within the medicine liquid receiving chamber  215  of the medicine barrel  21  to implement injection. In other embodiments not shown, the resilient actuation mechanism may be a pneumatic spring, airbag, or the like. 
     Specifically, the inner push rod  33  at the front end is provided with a front end flange  331   a  protruding radially outwards, and the resilient actuation mechanism includes an actuation spring  36  between the front end flange  331   a  and the base  31 , which is sleeved outside the inner push rod  33 . 
     Preferably, threads are provided between the outer housing  32  and the base  31 , and the outer housing  32  can move rearwards relative to the base  31  by means of threaded contact. Specifically, referring to  FIG.  11   , the base  31  includes a rear end portion and a base sidewall  312  extending forwards from the rear end portion, and the base sidewall  312  at its inner surface is provided with internal threads  312   a . The outer housing  32  at its rear outer surface is provided with external threads. Through cooperation of the internal and external threads, the outer housing  32  can stably compress the actuation spring  36  when moving rearwards relative to the base  31 . 
     Also preferably, the respective portions of the outer housing  32  and the inner push rod  33  facing the vial  1  in the radial direction may be configured to be at least partly transparent or hollow, making a volume of the medicine liquid within the vial  1  visible from outside. 
       FIGS.  14 - 20    show a process from mounting the needleless syringe  4  and the vial  1  until completing injection, which sequentially includes following main steps of: mounting, pressurized energy accumulating, medicine suctioning, and injecting. The respective steps will be sequentially described below with reference to the drawings. 
       FIG.  14    illustrates a schematic diagram of a process of mounting the injection head  2  and the vial  1  to the needleless syringe body  3 . As shown therein, the piston rod  22  of the injection head  2  is first inserted into the vial  1 , and the injection head  2  and the vial  1  then are mounted as a whole into the needleless syringe body  3 . When the vial  1  enters the inner push rod  33  and moves rearwards until it cannot be moved further, the piston rod  22  and the inner push rod  33  are engaged with each other, and the medicine barrel  21  and the outer housing  32  are screwed through threads. 
     The state of each component after assembling is shown in  FIG.  15   , where the needleless syringe  4  is in a ready-to-use state. In this state, the medicine barrel  21  is fixed relative to the outer housing  32 , the piston rod  22  and the vial  1  are fixed relative to the inner push rod  33 , and the locking mechanism  34  is still at an initial state, which has not locked the inner push rod  33  relative to the base  31  yet. 
     The process as shown in  FIGS.  15 - 16    is a pressurized energy accumulation process for the actuation spring  36 . Specifically, the outer housing  32  is rotated to move forwards relative to the base  31  (which is achieved through thread fit therebetween), and the front end  322  of the outer housing  32  can exert a force on the front end flange  331   a  of the inner push rod  33  thus to drive the inner pusher rod  33  to move rearwards simultaneously. When the outer housing  32  is screwed threadedly relative to the base  31 , the rear end flange  333  of the inner push rod  33  engages with the rear portion of the limiting member  344  such that the limiting member  344  abuts against the front surface of the rear end flange  333  to lock the inner push rod  33 . In the course, the actuation spring  36  is compressed to accumulate energy for the final injection step. 
     The process as shown in  FIGS.  16 - 17    is a medicine suctioning step. Specifically, the outer housing  32  is rotated to move forwards relative to the base  31  (which is achieved through thread fit therebetween), while the inner push rod  33  is fixed relative to the base  31  as being locked by the locking mechanism  34 . In other words, during this process, the outer housing  32  moves forwards relative to the inner push rod  33 . Since the medicine barrel  21  is fixed relative to the outer housing  32  and the vial  1  and the piston rod  22  are fixed relative to the inner push rod  33 , the medicine  21  moves forwards relative to the vial  1  and the piston rod  22 . Furthermore, since the injection micropore  211  of the medicine barrel  21  is closed by the cap  23 , the medicine liquid receiving chamber  215  is formed within the medicine barrel  21  when the medicine barrel  21  moves forwards relative to the piston rod  22 . Due to a small pressure within the medicine receiving chamber  215 , the liquid within the vial  1  is suctioned into the medicine liquid receiving chamber  215  via the medicine liquid channel  222   c  within the piston rod  22 , thereby completing medicine suctioning. 
     The step as shown in  FIG.  18    is an injection preparation step prior to the medicine suctioning step and the injection step, with the purpose of discharging gas probably mixed out of the medicine barrel  21  before injection. This step includes first removing the cap  23  to expose the injection micropore  211  and then rotating the outer housing  32  to move the same slightly rearwards relative to the base  31 , where the inner push rod  33  and the piston rod  22  are kept fixed relative to the base  31 . In the circumstance, the medicine barrel  21  actually moves slightly rearwards relative to the piston rod  22  to make the piston rod  22  gently compress the medicine liquid chamber  215  within the medicine barrel  21 , such that the gas within the medicine liquid receiving chamber  215  can be discharged from the injection micropore  211  as an effect of pressure. 
     The process as shown in  FIG.  19    is an injection step. At this step, the outer housing  32  and the medicine barrel  21  are fixed relative to the base  31 , and the inner push rod  33 , the vial  1 , and the piston rod  22  move forwards relative to the base  31  to compress the medicine liquid within the medicine liquid receiving chamber  215  via the piston rod  22 , thereby completing injection. Specifically, the injection step further includes an unlocking step and a resilient actuation step. 
     If injection is required, the button  341  at the rear end of the base  31  is pressed to move forwards. In the case, the protrusion portion  341   c  at the front end of the button  341  moves forwards to release radial restrictions on the limiting member  344  such that the limiting member  344  can move radially outwards to unlock the rear end flange  333  of the inner push rod  33 . In addition, along with the forward movement of the button  341 , the inner push rod  33  is driven to move forwards via the button spring  343  and the spring receiving portion. The inner push rod  33  passes over the limiting member  344 , causing the locking mechanism  34  to unlock the inner push rod  33 . 
     After unlocking, the inner push rod  33  can move forwards relative to the base  31 . At this time, the pressurized actuation spring  36  applies a large thrust to the front end flange  331   a  of the inner push rod  33  such that the inner push rod  33  drives the piston rod  22  to move forwards to push the medicine liquid within the medicine liquid receiving chamber  215  and thus eject the medicine liquid out of the injection micropore  211 . 
     As can be seen from the above-mentioned steps, the front end flange  331   a  of the inner push rod  33  is provided for at least two purposes: one is that, at the pressurized energy accumulation step, a force is applied to the front end flange  331   a  of the inner push rod  33  when the outer housing  32  moves rearwards relative to the base  31 , to drive the inner push rod  33  to move rearwards along therewith relative to the base  31  until reaching the locked position where the inner push rod  33  is locked by the locking mechanism; and the other is that, at the injection step, as being pressed between the base  31  and the front end flange  331   a  of the inner push rod  33 , the actuation spring  36  applies a thrust to the front end flange  331   a  to push the inner push rod  33  forwards to complete injection. 
       FIG.  20    shows a variation of the aforesaid embodiment. In the needleless syringe as shown in  FIG.  20   , the inner push rod  33  is provided with a middle flange  331   b , and the actuation spring  36  is pressed between the base  31  and the middle flange  331   b . In order to ensure that the actuation spring  36  is long enough to provide a sufficient actuation force, the inner push rod  33  is prolonged properly. Such arrangement prevents the actuation spring  36  from sheltering the vial  1  to make the volume within the vial visible from outside. 
       FIG.  21    shows a further variation of the aforesaid embodiment. In the needleless syringe as shown in  FIG.  21   , a spring shaft  37  is fixedly connected at the front end flange  331   a  of the inner push rod  33  of the needleless syringe body  3 , which extends rearwards from the front end flange  331   a  along a direction parallel to the axis X and is sheathed in the actuation spring  36 . Preferably, in order to apply a uniform thrust onto the inner push rod  33 , a plurality of spring shafts  37  may be provided, each being sheathed in an actuation spring  36 . The respective spring shafts  37  are arranged around the inner push rod  33  evenly or unevenly. 
     In  FIG.  21   , the needleless injection body  3  is provided therein with two spring shafts  37  which respectively extend along a direction Y and a direction Z being symmetrical with respect to the axis X. 
     Other components of the needleless syringe as shown in  FIGS.  20 - 21    are arranged similarly as those in  FIGS.  14 - 19   , and the description thereon is omitted here. 
       FIGS.  22 - 28    are schematic diagrams of cooperative use of the injection head  2  and the needleless syringe body according to a further embodiment. As shown in  FIG.  22   , the needleless syringe body  3  includes a base  31 , an outer housing  32 , and an inner push rod system  334 . Wherein, the base  31  includes a forward opening, the outer housing  32  includes a rearward opening and is mounted at the front end of the base  31  to form a receiving space between the base  31  and the outer housing  32 , and the outer housing  32  is provided with a front opening for fixedly mounting the medicine barrel  21 . The inner push rod system  334  includes an inner push rod  33  disposed within the receiving space and having a forward opening. The via  1  can be received within the inner push rod  33  and move along with the inner push rod  33 , and the piston rod  22  is fixedly mounted at the forward opening. 
     Preferably, the respective portions of the outer housing  32  and the inner push rod  33  facing the vial  1  in the radial direction can be configured to be at least partly transparent or hollow, to make the volume of the medicine liquid within the vial  1  visible from outside. 
     The connection relation among the above-mentioned components may be of multiple types. For example, a threaded connection may be provided between the outer housing  32  and the medicine barrel  21 . Referring to  FIG.  22   , the outer surface of the rear portion of the medicine barrel  21  is provided thereon with medicine-barrel external threads  213 , the front opening of the outer housing  32  is provided with in-housing internal threads  322   a , and the medicine-barrel external threads  213  can cooperate with the in-housing internal threads  322   a  to fix the medicine barrel  21  and the outer housing  32  relative to each other. The medicine barrel  21  may be provided with a limiting flange  212  for engagement on the front end face of the outer housing  32 . 
     The piston rod  22  may be cooperated with the inner push rod  33  in snap fit. Specifically, continuing with  FIG.  22   , the piston rod  22  at the outer surface is provided with a snap-fit protrusion  222   d , the inner push rod  33  at the corresponding position is provided with a snap-fit recess  33   a , and the snap-fit protrusion  222   d  is snap-fitted into the snap-fit recess  33   a  to secure the piston rod  22  relative to the inner push rod  33 . The rear portion  222   a  of the piston rod  22  may be of a large radial size to match the inner push rod  33 . Further, the space within the inner push rod  33  may be of a size adapted to the vial  1 , and after the piston rod  22  is snap-fitted with the inner push rod  33 , the vial  1  is adaptively disposed in the space which leaves no room for movement of the vial  1  relative to the inner push rod  33 . 
     As such, throughout the medicine suctioning and injection processes, the outer housing  32  is fixed relative to the medicine barrel  21 , the inner push rod  33  is fixed relative to both of the vial  1  and the piston rod  22 . But the outer housing  32 , the inner push rod  33  and the base  31  are movable relative to one other in the axis direction. Therefore, the outer housing  32  can drive the medicine barrel  21  to move, and the inner push rod  33  can drive the vial  1  and the piston  221  to move. 
     Specifically, the outer housing  32  can move in an anterior-posterior direction relative to the inner push rod system to drive the medicine barrel  21  to move in an front-rear direction relative to the vial  1  and the piston  22 , thereby implementing medicine suction and injection. More specifically, during the medicine suctioning process (see  FIG.  25   ), the inner push rod  33  is fixed relative to the base  31 , and the outer housing  32  moves forwards relative to the inner push rod  33 ; during the injection process (see  FIG.  27   ), the outer housing  32  is fixed relative to the base  31 , and the inner push rod system  334  moves forwards relative to outside inner push rod  33 . The specific medicine suction and injection process will be described below in detail. 
     Preferably, the needleless syringe body  3  further includes a locking mechanism  34  which is connected between the base  31  and the inner push rod system  334  to lock the inner push rod system  334  relative to the base  31  in the axial direction during the medicine suctioning process, and to unlock the same after medicine suction, causing the inner push rod system  334  to move forwards relative to the outer housing  32 . 
     Preferably, the outer housing  32  and the base  31  are connected in thread fit, to implement conversion of the relative rotation of the two into relative linear movement. Specifically, referring to  FIG.  8   , the base  31  includes a rear end portion and a base sidewall  312  extending forwards from the rear end portion, and the base sidewall  312  at its inner surface is provided with internal threads  312   a . The outer housing  32  at its rear outer surface is provided with external threads. With the cooperation of the internal and external threads, the rotation of the outer housing  32  relative to the base  31  can lead to front-rear movement relative to each other. 
     In order to accelerate the medicine suctioning rate in the medicine suctioning process, the needleless syringe body  3  further includes a medicine supply push rod  8  mounted at the rear end of the inner push rod  33 , and a front end of the medicine supply push rod  8  can be in contact with the cork of the vial. In order to transmit the relative movement between the outer housing  32  and the base  31  to the medicine supply push rod  8 , the needleless syringe body  3  further includes transmission means. A part of the transmission means is connected to the medicine supply push rod  8  while the other part of the transmission means is connected directly or indirectly to the base  31  or the outer housing  32 , to transmit specified relative movement between the base  31  and the outer housing  32  to the medicine supply push rod  8 . During the medicine suctioning process, the base  31  or the outer housing  32  drives, via the transmission means, the medicine supply push rod  8  to push the cork  12  forwards relative to the body of the vial  1  and thus compress the space within the vial  1 . 
     Preferably, the inner push rod system  334  further includes a transmission rod  335  cooperating with the transmission means, which is connected at a front end to the transmission means and engaged at a rear end  3351  with the locking mechanism  34 . When locked by the locking mechanism  34 , the transmission rod  335  is fixed relative to the base  31  in the rotational direction. A thrust bearing  7  is mounted between the transmission rod  335  and the inner push rod  33 . 
     It can be seen that, in the present embodiment, the transmission means is indirectly connected to the base  31  via the transmission rod  335 , so as to transmit the specified movement of the base  31  to the transmission means. However, in other embodiments not shown, there may not be a transmission rod  335 , and the base  31  may be directly connected to the transmission means. 
     Preferably, the axes of the transmission rod  335  and the medicine supply push rod  8  are the axis X of the needleless syringe body. A receiving chamber  332  of the medicine supply push rod (see  FIG.  29   ) extending along the axis X may be disposed within the transmission rod  335 , within which the medicine supply push rod  8  is mounted adaptively. The outer surface of the medicine supply push rod  8  is a threaded surface while the medicine supply push rod receiving chamber  332  has a smooth surface, such that the medicine supply push rod  8  can move along the axis direction within the medicine supply push rod receiving chamber  332 . 
     In the present embodiment, during the medicine suctioning process, the base  31  rotates to move forwards relative to the outer housing  32 , and the transmission means includes transmission means for rotational movement accordingly. The base  31  transmits the rotational movement via the transmission means for rotational movement to the medicine supply push rod  8  to drive the latter to rotate along therewith. In order to convert the rotational movement of the medicine supply push rod  8  into a linear movement and thus push the cork  12  forwards, a movement conversion mechanism is fixedly provided within the receiving space of the inner push rod  33 . A part of the movement conversion mechanism is engaged with the medicine supply push rod  8  while the other part is engaged with the inner push rod  33 , for conversion of the rotational movement of the medicine supply push rod  8  along with the base  31  relative to the outer housing (i.e., relative to the inner push rod  33 ) into a linear movement relative to the outer housing  32  along the axis direction. 
     The movement conversion mechanism, for example, may include a nut member  9  for engagement with the medicine supply push rod  8  in thread fit. In other embodiments not shown, the movement conversion mechanism may include other members capable of converting a relative rotational movement into a linear movement. 
     More preferably, the transmission means for rotational movement includes one-way transmission means for rotational movement. The one-way transmission means for rotational movement can only transmit one-way rotation of the transmission rod  335  to the medicine supply push rod  8 . More specifically, when the outer housing  32  rotates along a first rotational direction relative to the base  31  to move forwards relative to the same, the one-way transmission means for rotational movement can transmit the rotational movement of the transmission rod  335  to the medicine supply push rod  8 ; in turn, when the outer housing  32  rotates in a direction opposite to the first rotational direction relative to the base  31  to move rearwards relative to the same, the one-way transmission means for rotational movement can transmit the rotational movement of the transmission rod  335  to the medicine supply push rod  8 . 
     The one-way transmission means for rotational movement, for example, includes a one-way bearing. As shown in  FIGS.  30 A- 30 B , an outer ring  61  of the one-way bearing  6  is fixedly connected to the transmission rod  335 , and an inner ring  61  of the one-way bearing  6  is fixedly connected to the medicine supply push rod  8  in the rotational direction. On the contact surfaces of the inner ring  62  and the medicine supply push rod  8 , for example, a guide rod or keyway extending along the direction of the axis X may be provided to limit the relative rotation between the inner ring  62  and the medicine supply push rod  8 , without restricting the relative linear movement therebetween in the axis direction. 
     In the medicine suctioning process, the base  31  is rotated relative to the outer housing  32  to move the outer housing  32  forwards relative to the base  31 . During the rotational movement in the relative rotational direction, the outer ring  61  of the one-way bearing  6  can transmit the rotational movement to the inner ring  62 , so as to drive the medicine supply push rod  8  to rotate. The medicine supply push rod  8  rotates relative to the nut member  9  and thus moves forwards relative to the nut member  9  and further relative to the inner push rod  33  (at the time, the whole push rod system  334  is locked by the locking mechanism  34  in the axis direction), to push the cork  12  of the vial  1  and further cause the medicine liquid within the vial  1  to enter the medicine barrel  21 . 
     The transmission rod  335  at the rear part is provided with a rear end  3351  (see  FIG.  27   ) of the transmission rod  335  protruding radially outwards, which is formed in a flange structure and provided for cooperating with the locking mechanism  34 . The locking mechanism  34  includes a limiting member  344 , button  341 , spring receiving member  342 , and button spring  343 . In a locked state, the limiting member  344  can abut against the front end face of the rear end  3351  (which is formed in a flange structure) of the transmission rod  335  to limit the forward movement of the transmission rod  335 ; the button  341  is mounted at the rear end wall of the base  31  and protrudes rearwards relative to the base  31 ; the spring receiving member  342  is disposed between the rear end face of the transmission rod  335  and the rear end wall of the button  341 , which has a spring receiving chamber that opens rearwards; and the button spring  343  is disposed in the spring receiving chamber and configured to contact at its rear end with the button  341 . 
     In this way, the button  341  can be pushed, and the button spring  343  and the spring receiving member  342  in turn are pushed to directly push the transmission rod  335 . In the circumstance, the rear end  3351  (which is formed in a flange structure) of the transmission rod  335  can pass over the limiting member  344 , causing the locking mechanism  34  to unlock the transmission rod  335 . In other embodiment not shown, such members as the button spring  343 , the spring receiving member  342 , and the like may not be provided, and the button  341  can directly push the transmission rod  335 , causing the locking mechanism  34  to unlock the transmission rod  335 . 
     In the present embodiment, a movement limiting feature (not shown) is provided between the circumferential outer surface of the front end flange  331  of the inner push rod  33  and the circumferential inner surface of the outer housing  32 . The movement limiting feature is configured to limit rotation of the inner push rod  33  relative to the outer housing  32  while permitting front-rear movement of the inner push rod  33  relative to the outer housing  32  along the axis direction. The movement limiting feature, for example, may be a keyway or guide rod extending along the axis direction and disposed on the circumferential outer surface of the front end flange  331  and the circumferential inner surface of the outer housing  32 . 
     Owing to arrangement of the movement limiting feature, in the pressurized and medicine suctioning processes, the inner push rod  33  can rotate along with the outer housing  32 . However, when the inner push rod system  334  is wholly locked by the locking mechanism  34 , the inner push rod  33  can only rotate along with the outer housing  32 , being unable to move linearly. 
     The connection relation between the inner push rod  33  and the transmission rod  335  is of a specified type. Specifically, the circumferential outer surface of a transmission rod cooperating unit  3352  at the front end of the transmission rod  335  contacts and cooperates with the circumferential inner surface of the inner push rod  33 . There is a large sliding friction therebetween (for example, the two have rough contact surfaces). If one is not subjected to an external force, it rotates along with the other, and if both are subjected to an external force, the two rotate relative to each other. 
     Specifically, when the transmission rod  335  is not locked by the locking mechanism  34 , the transmission rod  335  can rotate along with the inner push rod  33 , for example, in the pressurized process, but the rotational direction is not the transmission direction of the one-way bearing  6 . Therefore, at this time, the rotation of the outer ring  61  of the one-way bearing  6  is not transmitted to the inner ring  62 . At this time, the medicine supply push rod  8  is driven by the nut member  9  (i.e., directly driven by the inner push rod  33 ) to move linearly, and no relative shift is generated between the medicine supply push rod  8  and the inner push rod  33 . When the transmission rod  335  is locked by the locking mechanism  34 , the transmission rod  335  can only rotate along with the locking mechanism  34 . For example, in the medicine suctioning process, the transmission rod  335  and the base  31  are consistent in rotational direction, the inner push rod  33  is consistent with the outer housing  32 , and there is relative rotation between the inner push rod  33  and the transmission rod  335 . However, since the inner push rod system  334  is wholly locked by the locking mechanism  34 , the inner push rod  33  only rotates relative to the transmission rod  335 , without translating relative to the same. 
       FIGS.  22 - 28    illustrate a process from mounting the needleless syringe  4  and the vial  1  until completing injection. The process sequentially includes main steps of: mounting, pressurized energy accumulating, medicine suctioning, and injecting. Reference will be made below to the drawings to describe the respective steps sequentially. 
       FIG.  22    illustrates a schematic diagram of a process of mounting the injection head  2  and the vial  1  to the needleless syringe body  3 . As shown therein, the piston rod  22  of the injection head  2  is first inserted into the vial  1 , and the injection head  2  and the vial  1  are subsequently mounted as a whole into the needleless syringe body  3 . When the vial  1  enters the inner push rod  33  and moves rearwards until it cannot be moved any longer, the piston rod  22  and the inner push rod  33  are engaged with each other, and the medicine barrel  21  and the outer housing  32  are screwed through threads. 
     The state of each component after assembling is shown in  FIG.  23   , where the needleless syringe  4  is in a ready-to-use state. In the state, the medicine barrel  21  is fixed relative to the outer housing  32 , the piston rod  22  and the vial  1  are fixed relative to the inner push rod  33 , and the locking mechanism  34  is still at an initial state, which has not locked the inner push rod  33  relative to the base  31  yet. 
     The process as shown in  FIGS.  23 - 24    is a pressurized energy accumulation process for the actuation spring  36 . Specifically, the outer housing  32  is rotated to move reawards relative to the base  31  (which is achieved through thread fit therebetween), and the front end portion  322  of the outer housing  32  can drive the inner push rod  33  to rotate along therewith while driving the inner push rod  33  to move rearwards. When the outer housing  32  is screwed threadedly relative to the base  31 , the rear end  3351  (which is formed in a flange structure) of the transmission rod  335  is engaged with the rear portion of the limiting member  344 , and at this time, the limiting member  344  abuts against the front surface of the rear end  3351  (which is formed in a flange structure) of the transmission rod  335  to lock the inner push rod system  334 . In the course, the actuation spring  36  is compressed to accumulate energy for the final injection step. 
     The process as shown in  FIGS.  24 - 25    is a medicine suctioning step. Specifically, the outer housing  32  is rotated to move forwards relative to the base  31  (which is achieved through thread fit therebetween), while the inner push rod  33  is fixed relative to the base  31  in the axial direction as being locked by the locking mechanism  34 . In other words, during this process, the outer housing  32  moves forwards relative to the inner push rod  33  (while rotating along therewith). Since the medicine barrel  21  is fixed relative to the outer housing  32  and the vial  1  and the piston rod  22  are fixed relative to the inner push rod  33 , the medicine  21  moves forwards relative to the vial  1  and the piston rod  22 . Furthermore, since the injection micropore  211  of the medicine barrel  21  is closed by the cap  23 , the medicine liquid receiving chamber  215  is formed within the medicine barrel  21  when the medicine barrel  21  moves forwards relative to the piston rod  22 . Due to a small pressure within the medicine receiving chamber  215 , the liquid within the vial  1  can be suctioned into the medicine liquid receiving chamber  215  via the medicine liquid channel  222   c  within the piston rod  22 , thereby completing medicine suctioning. 
     In the medicine suctioning process, the transmission rod  335  rotates along with the base  34  relative to the outer housing  32 , and the transmission rod  335  transmits the rotational movement via the one-way bearing  6  to the medicine supply push rod  8 . The medicine supply push rod  8  rotates relative to the nut member  9  and thus achieves forward movement relative to the nut member (i.e., relative to the inner push rod  33 ). The front end  81  (see  FIG.  22   ) of the medicine supply push rod  8  pushes the cork  12  to further compress the space within the via, to make the medicine liquid flow into the medicine liquid receiving chamber  215 . 
     The step as shown in  FIG.  26    is an injection preparation step prior to the medicine suctioning step and the injection step, with the purpose of discharging gas probably mixed out of the medicine barrel  21  before injection. This step includes first removing the cap  23  to expose the injection micropore  211  and then rotating the outer housing  32  to move the same slightly rearwards relative to the base  31 , where the inner push rod  33  and the piston rod  22  are kept fixed relative to the base  31 . In the circumstance, the medicine barrel  21  actually moves slightly rearwards relative to the piston rod  22  to gently compress the medicine liquid chamber  215  within the medicine barrel  21 , such that the gas within the medicine liquid receiving chamber  215  can be discharged from the injection micropore  211  as an effect of pressure. 
     The process as shown in  FIG.  27    is an injection step. At this step, the outer housing  32  and the medicine barrel  21  are fixed relative to the base  31 , and the inner push rod  33 , the vial  1 , and the piston rod  22  move forwards relative to the base  31  to compress the medicine liquid within the medicine liquid receiving chamber  215  via the piston rod  22 , thereby completing injection. Specifically, the injection step further includes an unlocking step and a resilient actuation step. 
     If injection is required, the button  341  at the rear end of the base  31  is pressed to move forwards. In the case, the protrusion portion  341   c  at the front end of the button  341  moves forwards to release radial restriction on the limiting member  344  such that the limiting member  344  can move radially outwards to unlock the rear end  3351  (which is formed in a flange structure) of the transmission rod  335 . In addition, along with the forward movement of the button  341 , the inner push rod system  334  is driven to move forwards via the button spring  343  and the spring receiving portion. The transmission rod  335  passes over the limiting member  344 , causing the locking mechanism  34  to unlock the inner push rod system  334 . 
     After unlocking, the inner push rod system  334  can move forwards relative to the base  31 . At this time, the pressurized actuation spring  36  applies a large thrust to the front end flange  331   a  of the inner push rod  33  such that the inner push rod  33  drives the piston rod  22  to move forwards to compress the medicine liquid within the medicine liquid receiving chamber  215  and thus eject the medicine liquid out of the injection micropore  211 . 
     As can be seen from the above-mentioned steps, the front end flange  331   a  of the inner push rod  33  is provided for at least two purposes: one is that, at the pressurized energy accumulation step, a force is applied to the front end flange  331   a  of the inner push rod  33  when the outer housing  32  moves rearwards relative to the base  31 , to drive the inner push rod  33  to move rearwards along therewith relative to the base  31  until reaching the locked position where the inner push rod  33  is locked by the locking mechanism  34 ; and the other is that, at the injection step, as being pressed between the base  31  and the front flange  331   a  of the inner push rod  33 , the actuation spring applies a thrust to the front end flange  331   a  to push the inner push rod  33  forwards to complete injection. 
     After one injection is completed, the vial  1  may not be removed for a next injection. In other words, the medicine liquid within the vial  1  may be provided for multiple injections. It would be appreciated that, after multiple injections, the cork  12  of the vial  1  will be continuously (which means continuously in space, rather than time) pushed forwards by the medicine supply push rod  8 .  FIGS.  28  and  29    illustrate the structure of the needleless syringe body after multiple injections. 
     In the circumstance, if pushed rearwards back to the initial position, the medicine supply push rod  8  may be rotated relative to the nut member  9 . In order to accelerate the operation, the nut member  9  may be preferably configured to allow the medicine supply push rod  8  to directly move rearwards relative to the nut member  9  while not rotating relative to the latter. 
     To this end, the nut member  9  may be configured as at least two nut members separate from each other, which can move radially outwards in a specified condition, thereby disengaging from the medicine supply push rod  8 .  FIGS.  31 - 34 B  illustrate three examples. 
     In the examples as shown in  FIGS.  31 - 34 B , at least two nut members are arranged around the medicine supply push rod  8 , and each can move radially towards or away from the axis to engage with or disengage from the medicine supply push rod  8 . 
     In the example as shown in  FIGS.  31 - 32 B , there are two nut members  9   a , each nut member  9   a  at the front end is provided with a nut limiting member  91   a , and the surface of the nut member  9   a  contacting with the limiting member  91   a  is a force bearing slope. Wherein, the rear end of the force bearing slope is farther away from the axis X of the needleless syringe in the radial direction than the front end. The nut limiting member  91   a  is a wedge which has a force applying slope contacting with the force bearing slope. 
     As shown in  FIG.  32 A , when mounted within the needleless syringe, the vial  1  can press the nut limiting member  91   a  rearwards, and the nut limiting member  91   a  exerts a force to the force bearing slope of the nut member  9   a . Since the pressure borne by the force bearing slope  9   a  is perpendicular to the slope, the pressure on the nut member  9   a  has an inward force component along the radial direction of the needleless syringe body, which presses the nut member  9   a  for engagement with the medicine supply push rod  8 . 
     As shown in  FIG.  32 B , when the vial  1  is removed, the nut limiting member  91   a  slides forwards to reduce the pressure applied to the nut member  9   a , such that the nut member  9   a  moves radially outwards to disengage from the medicine supply push rod  8 . At this time, the medicine supply push rod  8  can be directly pushed back to an initial position. 
     Preferably, the nut limiting member  91   a  at the rear end is further provided with a second limiting member  92   a  to prevent a exceedingly long rearward movement distance of the nut limiting member  91   a  which may bring about an excessively large force applied to the nut member  9   a.    
     The example in  FIGS.  33 A and  33 B  is similar to the one in  FIGS.  32 A and  32 B , but a nut limiting member  91   b  of an annular structure is used to replace to the wedge. The annular structure is coaxial with the needleless syringe body  3 , and a section after it is cut by a plane where the axis X is located (for example, in  FIGS.  33 A and  33 B ) is circular. In the embodiment, the contact between the nut limiting member  91   b  and the nut member  9   b  is point contact. 
     In the state as shown in  FIG.  33 A , as pressed rearwards by the vial  1 , the nut limiting member  91   b  compresses the nut member  9   b  into engagement with the medicine supply push rod  8 . As shown in  FIG.  33 B , the vial  1  was removed, the nut limiting member moves forwards, and the nut member  9   b  moves radially outwards to disengage from the medicine supply push rod  8 . 
     In addition, in embodiments not shown therein, the nut limiting member may be of a spherical structure, a sphere movement slot is provided correspondingly at a front end of a radial outer edge of the nut member, and the nut limiting member is limited within the sphere movement slot, making it impossible to escape therefrom. 
     The structure as shown in  FIGS.  34 A and  34 B  is a more preferable structure. In the example, the medicine supply push rod  8  applies an axial force to the nut member  9   c  (i.e., the medicine supply push rod  8  has a tendency of moving axially relative to the nut member  9   c , in case of not rotating relative to the same), and when the force reaches a predetermined threshold, the nut member  9   c  moves radially outwards, thereby not disengaging from the push rod. 
     In other words, when it is required to push the medicine supply push rod  8  back to the original position, only the medicine supply push rod  8  needs to be pushed, and the nut member  9   c  naturally moves radially outwards to permit axial translation of the medicine supply push rod  8 . 
     Moreover, the medicine supply push rod  8  can be subjected to a forward thrust, in addition to the rearward force, and when the thrust reaches a predetermined threshold, the nut member  9   c  moves radially outwards to disengage from the medicine supply push rod  8 . Specifically, the nut member  9   c  may disengage from the medicine supply push rod  8  in use when the thrust on the medicine supply push rod  8  is too great, thereby protecting the vial. 
     In connection with the injection head of the needleless syringe, the needleless syringe body, and the needleless syringe body assembly according to the present disclosure, the vial can be received within the needleless syringe body for a long time. And medicine suctioning and injection can be completed efficiently and effortlessly during each use, where there is no need for removing the vial or separating the medicine barrel from the vial. In the medicine suctioning process, the medicine supply push rod can push the cork forwards, so as to further improve the medicine suctioning efficiency. Furthermore, as the vial is received within the needleless syringe body, issues such as vial loss, contamination, and the like can be prevented. 
     Through the above disclosure, those skilled in the art would readily envisage using substitutes for the structures disclosed herein as feasible substitute embodiments, or combining the embodiments disclosed therein to form new embodiments. Such embodiments all fall into the scope claimed in the appended claims.