Dental syringe having an automatically retractable needle

A syringe including a hollow cylinder having an open proximal end and a substantially closed distal end, a pre-filled ampule loaded into said cylinder through the proximal end thereof, said ampule having a sealed cap at one end thereof, and a double ended hypodermic needle loaded into said cylinder ahead of said ampule and arranged in spaced axial alignment with said ampule, said syringe also including:

• a needle cartridge in which said double ended needle is carried, said needle cartridge having a hollow sleeve surrounding said needle and oppositely disposed proximal and distal ends for supporting said needle in axial alignment with said ampule;
• means for advancing said ampule axially and distally through said cylinder so that a proximal end of said needle penetrates the end cap of said ampule and a distal end of said needle projects outwardly from said cylinder past the distal end thereof;
• first locking means for releasably retaining said ampule at the distally advanced position within said cylinder;
• and
• said second locking means for retaining the end cap of said ampule interconnected with the proximal end of said needle to prevent the detachment thereof after said needle penetrates said end cap.

A syringe comprising a cylinder having an open proximal end and a substantially closed distal end and a fluid filled ampule loaded into said cylinder through the proximal end thereof, said syringe further comprising:

• a needle cartridge loaded into said cylinder ahead of said ampule, said cartridge supporting a double ended hypodermic needle in spaced axial alignment with said ampule;
• a hollow collar surrounding at least some of said ampule and capable of being moved distally through said syringe cylinder for correspondingly advancing said ampule distally through said cylinder and towards said needle cartridge such that a proximal end of said needle penetrates said ampule and a distal end of said needle extends outwardly from said cartridge and past the distal end of said cylinder so that the contents of said ampule can be expulsed therefrom;
• and
• locking means movable to a locked position by which to releasably retain said ampule at the distally advanced position with said cylinder or movable to an unlocked position by which to release said ampule from the distally advanced position, so that said ampule can be disposed proximally through said cylinder and said needle retracted back into said cartridge.

A syringe comprising a cylinder having an open proximal end and a substantially closed distal end and a fluid filled ampule loaded into said cylinder through the proximal end thereof, said syringe further comprising:

• a needle cartridge loaded into said cylinder ahead of said ampule, said cartridge including a double ended hypodermic needle supported in spaced axial alignment with said ampule, said needle cartridge also including a sleeve surrounding said needle and having oppositely disposed proximal and distal ends for supporting said needle and compression spring means extending between said proximal and distal ends;
• means for advancing said ampule distally through said cylinder and into engagement with said needle cartridge such that a proximal end of said needle penetrates said ampule and a distal end of said needle extends outwardly from said cartridge and past the distal end of said cylinder so that the contents of said ampule can be expulsed therefrom, the distal advancement of said ampule through said cylinder and into engagement with said cartridge also driving the proximal end of said sleeve toward the distal end thereof to compress said spring means therebetween and force the distal end of said needle outwardly from said sleeve and past the distal end of said cylinder so that an injection may be administered;
• locking means movable to a locked position by which to releasably retain said ampule at the distally advanced position with said cylinder or movable to an unlocked position by which to release said ampule from the distally advanced position, so that said ampule can be disposed proximally through said cylinder and said needle retracted back into said cartridge;
• and
• said spring means returning to the relaxed condition for driving the proximal end of said sleeve away from the distal end thereof to retract said needle within said cartridge sleeve when said locking means releases said ampule from said distally advanced position.

A syringe including a hollow cylinder having an open proximal end and a substantially closed distal end, a pre-filled ampule loaded through the proximal end of said cylinder and movable therethrough, a needle cartridge loaded into said cylinder ahead of said ampule and movable through said cylinder, said cartridge supporting a double ended hypodermic needle in spaced axial alignment with said ampule, said syringe further including:

• first locking means by which to releasably engage and retain said needle cartridge at a relatively proximal position within said cylinder;
• means for moving said ampule into contact with said needle cartridge and into fluid communication with a proximal end of said needle thereof while said cartridge is retained at said relatively proximal position;
• second locking means for preventing the detachment of said ampule from the needle of said needle cartridge;
• third locking means by which to engage and retain said needle cartridge at a relatively distal position within said cylinder after said first locking means has released said cartridge from the relatively proximal position and said cartridge and ampule have been advanced distally through said cylinder;
• and
• fourth locking means by which to releasably engage and retain said ampule at said distally advanced position within said cylinder, such that a distal end of said needle is forced outwardly from said cartridge and past the distal end of said cylinder, the distal end of said needle being retracted back into said cartridge when said fourth locking means releases said ampule from said distally advanced position.

A syringe comprising a cylinder having an open proximal end and a substantially closed distal end and a fluid filled ampule loaded into said cylinder through the proximal end thereof, said syringe further comprising:

• a needle cartridge loaded into said cylinder ahead of said ampule, said needle carrying cartridge including an outer sleeve surrounding a double ended needle and having means to retain said needle in spaced axial alignment with said ampule;
• means for advancing said ampule axially and distally through said cylinder in a direction towards said cartridge until a first end of said needle penetrates said ampule and the opposite end of said needle is moved outwardly from the sleeve of said cartridge to project past the distal end of said cylinder for administering an injection;
• and
• locking means movable to either a locked position by which to releasably retain said ampule at the distally advanced position with said needle projecting from said cylinder or to an unlocked position by which to release said ampule from said distal position so that said needle can be retracted back into the sleeve of said cartridge.