Syringe and method for assembling it

Abstract

A syringe comprising: a body delimiting a chamber; a piston able to slide in the chamber of the body along a longitudinal axis of the syringe, wherein the piston comprises a rod, a head, and a finger rest, which are all in one piece; and a deformable retention device designed to prevent the piston from leaving the body entirely, wherein the retention device is force-fitted in the chamber, extends around the piston over an angular sector strictly greater than 180° when it is in the assembled position, and has protruding external ribs which extend parallel to the longitudinal axis and are plastically deformable when the retention device is assembled in the chamber.

The invention claimed is: 
     
       1. A syringe comprising:
 a body delimiting a chamber; 
 a piston able to slide in the chamber of the body along a longitudinal axis of the syringe, the piston comprising a rod, a head and a finger rest, which are all in one piece, the head of the piston having a diameter that is sealingly received in a diameter of the chamber; and 
 a retention device that is deformable, 
 wherein the retention device is force-fitted assembled in the chamber, 
 wherein the retention device extends around the rod of the piston over an angular sector strictly greater than 180° when the retention device is assembled in the chamber, wherein the retention device is designed to come in contact with the head of the piston to prevent the piston from leaving the body entirely when the retention device is assembled in the chamber, 
 wherein when the retention device is assembled in the chamber, the retention device has a passage into which the rod is received and into which the rod is axially movable for any angular position of the piston around the longitudinal axis, and 
 wherein the retention device has no arrangement locking the retention device into a fixed closed ring form but comprises two C-shaped parts connected to each other by a thinned area which is deformable and which induces a spring effect between the C-shaped parts so as to make the retention device exert a radial force towards outside of the body when the retention device is assembled in the chamber, 
 wherein the retention device has protruding external ribs, which extend parallel to the longitudinal axis and which are plastically deformable when the retention device is assembled in the chamber, and 
 wherein the retention device excluding the external ribs has a maximum transverse outside dimension that is less than the diameter of the chamber when the retention device is assembled in the chamber. 
 
     
     
       2. The syringe of  claim 1 , wherein the body is made of a plastic material having a Young's modulus strictly greater than 1600 MPa. 
     
     
       3. The syringe of  claim 1 , wherein the retention device is force-fitted assembled axially in the chamber. 
     
     
       4. The syringe of  claim 1 , wherein the retention device comprises two C-shaped parts connected to each other by a deformable thinned area. 
     
     
       5. The syringe of  claim 1 , wherein the head has a diameter that is at least 10% greater than a diameter of the passage when the retention device is assembled in the chamber. 
     
     
       6. The syringe of  claim 1 , wherein the external ribs are arranged on the retaining device and distributed at a distance from one another around the longitudinal axis. 
     
     
       7. The syringe of  claim 1 , wherein at each of the external ribs, the retention device has a maximum outside transverse dimension that is strictly greater than a diameter of the chamber when the retention device is assembled in the chamber. 
     
     
       8. The syringe of  claim 1 , wherein the body is provided with a housing leading into the chamber, and wherein the retention device includes at least one external clip which is engaged transversely in a housing of the body when the retention device is assembled in the chamber adapted:
 when the retention device is assembled in the chamber, to be received in the housing, and 
 when force-fitting the retention device in the chamber, to be urged radially toward the longitudinal axis by the body, until reaching the housing into which the at least one external clip engage transversely to the longitudinal axis by stress releasing. 
 
     
     
       9. The syringe of  claim 1 , wherein the passage includes a lateral entry opening having a width that is less than a diameter of the rod both before and when the retention device is assembled in the chamber. 
     
     
       10. The syringe of  claim 1 , wherein the head includes a sealing element. 
     
     
       11. The syringe of  claim 10 , wherein the head includes a groove in which the sealing element is disposed. 
     
     
       12. The syringe of  claim 10 , wherein the sealing element is an integral part of the head. 
     
     
       13. The syringe of  claim 1 , wherein the volume of the chamber is less than 25 mL. 
     
     
       14. A method for assembling the syringe of  claim 1 , the method comprising:
 (a) deforming the retention device the thinned area to move the two C-shaped parts away from each other and then to move the two C-shaped parts toward each other so as to mount the retention device around the rod; 
 (b) inserting the piston with the retention device mounted around the rod in the chamber; and 
 (c) force fitting the retention device in the chamber. 
 
     
     
       15. The method of  claim 14 , wherein step (c) further comprises assembling the retention device to the body by a translation movement, that is coaxial with the longitudinal axis. 
     
     
       16. The syringe of  claim 1 , wherein in a geometrical plane that is perpendicular to the longitudinal axis, a minimum dimension of the passage is strictly greater than a maximum dimension of the rod all along the rod. 
     
     
       17. The syringe of  claim 1 , wherein the retention device has a surface which is perpendicular to the longitudinal axis and which is designed to come in contact with the head to prevent the piston from leaving the body entirely when the retention device is assembled in the chamber. 
     
     
       18. A syringe comprising:
 a body delimiting a chamber; 
 a piston able to slide in the chamber of the body along a longitudinal axis of the syringe, the piston comprising a rod, a head and a finger rest, which are all in one piece, the head of the piston having a diameter that is sealingly received in a diameter of the chamber; and 
 a retention device that is deformable, 
 wherein the retention device is force-fitted assembled in the chamber, 
 wherein the retention device extends around the rod of the piston over an angular sector strictly greater than 180° when the retention device is assembled in the chamber, 
 wherein the retention device has a surface which is perpendicular to the longitudinal axis, which has a closed ring shape and which is designed to come in contact with the head to prevent the piston from leaving the body entirely when the retention device is assembled in the chamber, and 
 wherein the retention device comprises two C-shaped parts connected to each other by a thinned area that is deformable,  
 wherein the retention device has protruding external ribs, which extend parallel to the longitudinal axis and which are plastically deformable when the retention device is assembled in the chamber, and 
 wherein the retention device excluding the external ribs has a maximum transverse outside dimension that is less than the diameter of the chamber when the retention device is assembled in the chamber. 
 
     
     
       19. The syringe of  claim 18 , wherein when the retention device is assembled in the chamber, the retention device has a passage into which the rod is received and into which the rod is axially movable for any angular position of the piston around the longitudinal axis. 
     
     
       20. The syringe of  claim 18 , wherein the body is made of a plastic material having a Young's modulus strictly greater than 1600 MPa. 
     
     
       21. The syringe of  claim 18 , wherein the retention device is force-fitted assembled axially in the chamber. 
     
     
       22. The syringe of  claim 18 , wherein the retention device comprises two C-shaped parts connected to each other by a deformable thinned area. 
     
     
       23. The syringe of  claim 18 , wherein the external ribs are arranged on the retaining device and distributed at a distance from one another around the longitudinal axis. 
     
     
       24. The syringe of  claim 18 , wherein at each of the external ribs, the retention device has a maximum outside transverse dimension that is strictly greater than a diameter of the chamber when the retention device is assembled in the chamber. 
     
     
       25. The syringe of  claim 18 , wherein the volume of the chamber is less than 25 mL. 
     
     
       26. A method for assembling the syringe of  claim 18 , the method comprising:
 (a) deforming the retention device the thinned area to move the two C-shaped parts away from each other and then to move the two C-shaped parts toward each other so as to mount the retention device around the rod; 
 (b) inserting the piston with the retention device mounted around the rod in the chamber; and 
 (c) force fitting the retention device in the chamber. 
 
     
     
       27. The method of  claim 26 , wherein step (c) further comprises assembling the retention device to the body by a translation movement, that is coaxial with the longitudinal axis. 
     
     
       28. The syringe of claim 18, wherein the body is provided with a housing leading into the chamber, and wherein the retention device includes at least one external clip which is adapted:
 when the retention device is assembled in the chamber, to be received in the housing, and   when force-fitting the retention device in the chamber, to be urged radially toward the longitudinal axis by the body, until reaching the housing into which the at least one external clip engage transversely to the longitudinal axis by stress releasing.   
     
     
       29. The syringe of claim 18, wherein the retention device has no arrangement locking the retention device into a fixed closed ring form, and wherein the thinned area induces a spring effect between the C-shaped parts so as to make the retention device exert a radial force towards outside of the body when the retention device is assembled in the chamber. 
     
     
       30. A method for assembling a syringe,
 the syringe comprising:
 a body delimiting a chamber; 
 a piston able to slide in the chamber along a longitudinal axis of the syringe, the piston comprising a rod, a head and a finger rest, which are all in one piece the head of the piston having a diameter that is sealingly received in a diameter of the chamber; and 
 a retention device that is deformable, 
 wherein the retention device is force-fitted assembled in the chamber, 
 wherein the retention device extends around the rod of the piston over an angular sector strictly greater than 180° when the retention device is assembled in the chamber, wherein the retention device is designed to come in contact with the head of the piston to prevent the piston from leaving the body entirely when the retention device is assembled in the chamber, 
 wherein when the retention device is assembled in the chamber, the retention device has a passage into which the rod is received and into which the rod is axially movable for any angular position of the piston around the longitudinal axis, 
 wherein the retention device comprises two C-shaped parts connected to each other by a thinned area that is deformable, 
 wherein the retention device has protruding external ribs, which extend parallel to the longitudinal axis and which are plastically deformable when the retention device is assembled in the chamber, and 
   wherein the retention device excluding the external ribs has a maximum transverse outside dimension that is less than the diameter of the chamber when the retention device is assembled in the chamber,   and the method comprising:   (a) deforming the thinned area to move the two C-shaped parts away from each other and then to move the two C-shaped parts toward each other so as to mount the retention device around the rod;   (b) inserting the piston with the retention device mounted around the rod in the chamber; and   (c) force fitting the retention device in the chamber.