Device for locking a plunger rod of a syringe after use and preventing re-use of the syringe, and syringe assembly

1. A locking device for locking a plunger rod of a syringe after use and preventing re-use of the syringe, wherein

the syringe includes a barrel having an open proximal end and a flange provided adjacent said open proximal end, wherein the barrel is configured to receive the plunger rod through said open proximal end and a proximal end of the plunger rod is formed disc-shaped and the flange is relatively slim in a direction transverse to a longitudinal direction of the barrel,

said locking device comprising

a mounting portion configured for mounting the locking device to the flange adjacent said open proximal end of the barrel by positive-fit by pushing the mounting portion onto the flange along the direction transverse to the longitudinal direction of the barrel and clipping the mounting portion onto the flange, and

a plunger rod locking portion for locking an axial position of the plunger rod after use of the syringe, wherein

an outer width of the mounting portion is larger than an outer width of the flange so that the mounting portion is configured to serve as a finger rest during use of the syringe,

a communication channel is formed in the locking device for enabling insertion of the plunger rod into the open proximal end of the barrel via the plunger rod locking portion and the mounting portion; wherein

a width of the communication channel is larger inside the plunger rod locking portion to form a chamber for receiving the disc-shaped proximal end of the plunger rod after use of the syringe, and

the plunger rod locking portion comprises a plurality of positive locking devices configured to positively lock the axial position of the plunger rod by positive-fit engagement with the disc-shaped proximal end of the plunger rod, for locking the plunger rod at or near a foremost axial position of a distal end of the plunger rod in the barrel after use of the syringe; wherein

the chamber formed by the plunger rod locking portion is configured for preventing full access to the disc-shaped proximal end of the plunger rod from outside the plunger rod locking portion, to prevent withdrawal of the disc-shaped proximal end of the plunger rod out of the chamber, when the axial position of the plunger rod is positively locked,

the plunger rod locking portion is formed as a cage-like cylindrical member formed by two annular webs interconnected by a plurality of axial connecting webs, wherein each positive locking device of the plurality of positive locking devices is provided on an inner side of an annular web or of an axial connecting web, and

a width of the communication channel is reduced at least in sections to a width that is smaller than an outer diameter of a plunger used for sealing the barrel, for preventing inadvertent removal of the plunger from the barrel via the communication channel.

2. The locking device as claimed in claim 1 , wherein a stop surface is provided at a bottom of said chamber for defining the foremost axial position of the distal end of the plunger rod in the barrel by abutment of the disc-shaped proximal end of the plunger rod with the stop surface.

3. The locking device as claimed in claim 1 , wherein the plurality of positive locking devices is configured to retain the disc-shaped proximal end of the plunger rod inside the chamber and to prevent withdrawal of the disc-shaped proximal end of the plunger rod toward a proximal end of the plunger rod locking portion beyond a minimum distance to a proximal upper rim of the plunger rod locking portion, when the axial position of the plunger rod is positively locked, wherein the minimum distance corresponds at least to an axial length of the at least one positive locking device.

4. The locking device as claimed in claim 1 , wherein each positive locking device of the plurality of positive locking devices is formed as a locking nose radially protruding into the plunger rod locking portion and being configured for positive-fit engagement with the disc-shaped proximal end of the plunger rod.

5. The locking device as claimed in claim 4 , wherein each locking nose is configured to be resiliently deformed or flexed when the disc-shaped proximal end of the plunger rod is pushed beyond the at least one locking nose before the distal end of the plunger rod reaches its foremost axial position in the barrel.

6. The locking device as claimed in claim 4 , wherein each locking nose is formed at a window, which is formed in the plunger rod locking portion such that the chamber communicates with an outside of the plunger rod locking portion.

7. The locking device as claimed in claim 4 , wherein the each locking nose has a beveled upper surface facing towards a proximal open end of the plunger rod locking portion and a bottom side extending radially inwards into the chamber formed by the plunger rod locking portion.

8. The locking device as claimed in claim 1 , wherein a height of the chamber formed by the plunger rod locking portion in an axial direction of the device is equal to a thickness of the disc-shaped proximal end of the plunger rod; or is larger than a thickness of the disc-shaped proximal end of the plunger rod.

9. The locking device as claimed in claim 1 , wherein the mounting portion comprises an upper plate directed towards the proximal end of the communication channel and a bottom plate opposite to said upper plate, an interspace being formed between the upper and bottom plate, wherein at least one protrusion is formed at a proximal end of the mounting portion protruding from the upper plate into the interspace and configured for positive-fit engagement with the open proximal end of the barrel, for mounting the locking device on the flange of the barrel.

10. The locking device as claimed in claim 9 , wherein at least a bottom end of the at least one protrusion facing the bottom plate of the mounting portion is resilient.

11. The locking device as claimed in claim 9 , wherein the at least one protrusion has a tapered profile having an outer diameter corresponding to the inner diameter of the barrel at the open proximal end, wherein a height of the interspace formed between the upper and bottom plate of the mounting portion preferably corresponds to a height of the flange at the open proximal end of the barrel.

12. The locking device as claimed in claim 1 , further comprising at least one protrusion provided in the communication channel reducing the width of the communication channel at least in sections to a width that is smaller than an outer diameter of a plunger used for sealing the barrel, for preventing inadvertent removal of the plunger from the barrel via the communication channel.

13. The locking device as claimed in claim 1 , wherein the plurality of axial connecting webs are provided at equidistant spacing along a circumferential direction of the two annular webs, wherein each of the plurality of positive locking devices radially protrudes into the plunger rod locking portion to thereby form a locking structure of an opening width, which is slightly less than a maximum outer width of the disc-shaped proximal end of the plunger rod, wherein each of the plurality of locking noses has a beveled upper surface facing towards a proximal open end of the plunger rod locking portion under an acute angle.

14. A syringe assembly comprising:

a syringe barrel pre-filled with a selected dose of medication and having a distal end, an open proximal end opposite to the distal end, a sidewall extending between the distal end and the open proximal end defining a chamber, and a flange provided adjacent said open proximal end, the flange being relatively slim in a direction transverse to a longitudinal direction of the barrel;

a plunger disposed within the chamber of the syringe barrel;

a plunger rod associated with the plunger and connected with the plunger, a proximal end of the plunger rod being formed disc-shaped; and

a locking device, which is mounted to the flange adjacent said proximal end by positive-fit, for locking the plunger rod at or near a foremost axial position of the distal end of the plunger rod in the barrel after use of the syringe and preventing re-use of the syringe; wherein

said locking device comprises

a mounting portion clipped onto the flange adjacent said open proximal end of the syringe barrel by positive-fit by pushing the mounting portion onto the flange along the direction transverse to the longitudinal direction of the syringe barrel, and

a plunger rod locking portion for locking the axial position of the plunger rod after use of the syringe, wherein

an outer width of the mounting portion is larger than an outer width of the flange so that the mounting portion is configured to serve as a finger rest during use of the syringe,

a communication channel is formed in the locking device for enabling insertion of the plunger rod into the open proximal end of the barrel via the plunger rod locking portion and the mounting portion; wherein

a width of the communication channel is larger inside the plunger rod locking portion to form a chamber for receiving the disc-shaped proximal end of the plunger rod after use of the syringe, and

the plunger rod locking portion comprises a plurality of positive locking devices configured to positively lock the axial position of the plunger rod by positive-fit engagement with the disc-shaped proximal end of the plunger rod, for locking the plunger rod at or near a foremost axial position of a distal end of the plunger rod in the syringe barrel after use of the syringe; wherein

the chamber formed by the plunger rod locking portion is configured for preventing full access to the disc-shaped proximal end of the plunger rod from outside the plunger rod locking portion, to prevent withdrawal of the disc-shaped proximal end of the plunger rod out of the chamber, when the axial position of the plunger rod is positively locked,

the plunger rod locking portion is formed as a cage-like cylindrical member formed by two annular webs interconnected by a plurality of axial connecting webs, wherein each positive locking device of the plurality of positive locking devices is provided on an inner side of an annular web or of an axial connecting web, and

a width of the communication channel is reduced at least in sections to a width that is smaller than an outer diameter of a plunger used for sealing the barrel, for preventing inadvertent removal of the plunger from the barrel via the communication channel.

15. The syringe assembly as claimed in claim 14 , wherein each positive locking device is formed as a locking nose radially protruding into the plunger rod locking portion and being configured for positive-fit engagement with the disc-shaped proximal end of the plunger rod.

16. The syringe assembly as claimed in claim 15 , wherein each locking nose is configured to be resiliently deformed or flexed when the disc-shaped proximal end of the plunger rod is pushed beyond the at least one locking nose before the distal end of the plunger rod reaches its foremost axial position in the barrel.

17. The syringe assembly as claimed in claim 14 , wherein the plurality of axial connecting webs are provided at equidistant spacing along a circumferential direction of the two annular webs, wherein each of the plurality of positive locking devices radially protrudes into the plunger rod locking portion to thereby form a locking structure of an opening width, which is slightly less than a maximum outer width of the disc-shaped proximal end of the plunger rod, wherein each of the plurality of locking noses has a beveled upper surface facing towards a proximal open end of the plunger rod locking portion under an acute angle.

18. A locking device for locking a plunger rod of a syringe after use and preventing re-use of the syringe, wherein

the syringe includes a barrel having an open proximal end and a flange provided adjacent said open proximal end, wherein the barrel is configured to receive the plunger rod through said open proximal end and a proximal end of the plunger rod is formed disc-shaped,

said locking device comprising

a mounting portion configured for mounting the locking device to the flange adjacent said open proximal end of the barrel by positive-fit by pushing the mounting portion onto the flange along the direction transverse to the longitudinal direction of the barrel and clipping the mounting portion onto the flange, and

a plunger rod locking portion for locking an axial position of the plunger rod after use of the syringe, wherein

a communication channel is formed in the locking device for enabling insertion of the plunger rod into the open proximal end of the barrel via the plunger rod locking portion and the mounting portion; wherein

a width of the communication channel is larger inside the plunger rod locking portion to form a chamber for receiving the disc-shaped proximal end of the plunger rod after use of the syringe,

the plunger rod locking portion comprises a plurality of positive locking devices configured to positively lock the axial position of the plunger rod by positive-fit engagement with the disc-shaped proximal end of the plunger rod, for locking the plunger rod at or near a foremost axial position of a distal end of the plunger rod in the barrel after use of the syringe, and

the plunger rod locking portion is formed as a cage-like cylindrical member formed by two annular webs interconnected by a plurality of axial connecting webs, wherein each positive locking device of the plurality of positive locking devices is provided on an inner side of an annular web or of an axial connecting web.