NEEDLE COVERING MECHANISM, NEEDLE HOLDER AND HYPODERMIC SYRINGE

摘要

1. A needle covering mechanism (1,1') for a hypodermic syringe (2, 2') comprising a barrel (7, 7') for an injectant and a plunger (31) for expelling the injectant from the barrel (7, 7'), the needle covering mechanism (1, 1') comprises a protective cover sleeve (4) which is movable between a retracted position in which a needle (27) is exposed and an extended position in which the needle (27) is covered, a helical compression spring (8) located inside the cover sleeve (4) for biasing the cover sleeve (4) towards the extended position, a lock for keeping the cover sleeve (4) in the retracted position, and a release mechanism for releasing the lock, the needle covering mechanism (1,1') is characterised by: a body (3, 3') with a cover sleeve retraction chamber (10), which body (3, 3') in a first end (5, 5') is adapted to receive injectant from the barrel (7, 7') and in a second end (6) has an opening for the cover sleeve (4), the cover sleeve (4) being slidingly supported inside the body (3, 3'), enabling movement of the cover sleeve (4) between the extended position and the retracted position essentially inside the retraction chamber (10), a retainer (9) for the cover sleeve (4), slidingly supported inside the cover sleeve (4), the retainer (9) comprises an external sliding surface (12), a base portion (15) for fixing and supporting the needle (27), an abutting portion (13) for the helical spring (8), a first radially compressible portion (14) with first detents (16) which in a non-compressed position projects radially out from the sliding surface (12) of the retainer (9) and in a compressed position are flush or within the sliding surface (12), a second radially compressible portion (21) with second detents (22) which in a non-compressed position projects radially out from the sliding surface (12) of the retainer (9) and in a compressed position are flush or within the sliding surface (12), a spacer (11) for maintaining the first radially compressible portion (14) of the retainer (9) in the non-compressed position, made from a material which after some time in contact with the injectant loses its mechanical strength, and a trigger (20, 20'), slidingly supported inside the body (3, 3'), comprising a funnel-shaped portion (18) facing the first radially compressible portion (14) of the retainer (9), wherein, in an operating position of the needle covering mechanism (1, 1'), the cover sleeve (4) is located essentially inside the retraction chamber (10) and the compression spring (8) is tensioned and biases the first radially compressible portion (14) of the retainer (9) towards the funnel-shaped portion (18) of the trigger (20, 20'), the trigger (20, 20') abuts stoppers (23, 23') fixed relative to the body (3, 3'), preventing a movement of the trigger (20, 20') towards the syringe barrel (7, 7'), the second detents (22) of the retainer (9) engage indentations (24) fixed relative to the body (3, 3'), preventing a movement of the retainer (9) away from the syringe barrel (7, 7'), and the first detents (16) of the retainer (9) engage indentations (25) in the cover sleeve (4), preventing a movement of the cover sleeve (4) towards the extended position, whereupon a contact between the spacer (11) and the injectant causes the spacer (11) to lose its mechanical strength and deform, the compression spring (8) forces the first radially compressible portion (14) of the retainer (9) into the funnel-shaped portion (18) of the trigger (20, 20') and thus into the compressed position, the first detents (16) slip out of the indentations (25) in the cover sleeve (4), thereby releasing the cover sleeve (4) from the retracted position, and the spring (8) forces the cover sleeve (4) to the extended position. 2. A needle covering mechanism (1, 1') according to claim 1, characterized in that the trigger (20, 20') comprises a head (26, 26') which in the operating position of the needle covering mechanism (1, 1') projects into the syringe barrel (7, 7') and forms an abutment for the plunger (31) when the plunger (31) is close to the bottom (35) of the barrel (7, 7'), whereupon a further movement of the plunger (31) towards the bottom (35) of the barrel (7, 7') moves the trigger (20, 20') towards the retainer (9), causing the funnel-shaped portion (18) of the trigger (20, 20') to force the first compressible portion (14) of the retainer (9) into the compressed position, thereby deforming the spacer (11), the first detents (16) of the retainer (9) slip out of the indentations (25) in the cover sleeve (4), thereby releasing the cover sleeve (4) from the retracted position, and the spring (8) forces the cover sleeve (4) to the extended position. 3. A needle covering mechanism (1, 1') according to claim 2, characterized in that, in the operating position of the needle covering mechanism (1, 1'), the cover sleeve (4) abuts the trigger (20, 20'), whereupon a movement of the trigger (20, 20') towards the retainer (9) causes the cover sleeve (4) to move towards the extended position, thereby assisting in releasing the cover sleeve (4) from the retracted position by forcing the first detents (16) out of the indentations (25) in the cover sleeve (4). 4. A needle covering mechanism (1, 1') according to any of the preceding claims, characterised in that the first radially compressible portion (14) of the retainer (9) comprises first elastic arms which extend from the base portion (15) of the retainer (9) and in their free ends (28) are moveable between the compressed and non-compressed position. 5. A needle covering mechanism (1, 1') according to claim 4, characterised in that the free ends (28) of the first elastic arms (14) have oblique end faces (17), corresponding to the funnel-shaped portion (18) of the trigger (20, 20'). 6. A needle covering mechanism (1, 1') according to claim 4 or 5, characterised in that the first elastic arms (14) have mountings (29) for the spacer (11). 7. A needle covering mechanism (1, 1') according to any of the claims 4-6, characterised by two first elastic arms (14) and a spacer (11) formed by a bolt which is mounted between the first elastic arms (14). 8. A needle covering mechanism (1, 1') according to any of the preceding claims, characterised in that the spacer (11) is made from alginate. 9. A needle covering mechanism (1, 1') according to any of the claims 1-8, characterised in that the spacer (11) is made from a water soluble polymer. 10. A needle covering mechanism (1, 1') according to any of the preceding claims, characterised in that the second radially compressible portion (21) of the retainer (9) comprises second elastic arms which extend from the base portion (15) of the retainer (9) and in their free ends (30) are moveable between the compressed and non-compressed position. 11. A needle covering mechanism (1, 1') according to any of the preceding claims, characterized in that sealing between the cover sleeve (4) and the body (3) and retainer (9), respectively, is achieved by sealings which are co-injected with the cover sleeve (4). 12. A needle holder (34) for a hypodermic syringe (2), characterised in comprising a needle covering mechanism (1) according to any of the claims 1-10, in which the first end (5) of the body (3) is adapted to match an outlet (19) from a syringe barrel (7). 13. A needle holder (34) for a hypodermic syringe (2) according to claim 11, characterised in that the trigger (20) comprises a rod (32) which in the operating position of the needle covering mechanism (1) extend through the barrel outlet (19), the end of the rod (32) forming the trigger head (26). 14. A needle holder (34) for a hypodermic syringe (2) according to claim 12, characterised in that the rod (32) is provided with splines (33) providing channels for the injectant. 15. A hypodermic syringe (2') comprising a barrel (7') and a plunger (31), characterised in comprising a needle covering mechanism (1') according to any of the claims 1-10, in which the first end (5') of the body (3') forms an integral extension of the barrel (7').