Details for Patent: 6,235,004

Title:	Injection syringe
Abstract:	The present invention provides an injection syringe comprises a housing including a holder for containing a cartridge of medicine, a piston rod with a non-circular cross-section having an outer thread, a piston rod drive, a one way coupling having an annular ring of internal ratchet notches, which annular ring can be integral with the housing, and a pawl having at least a pair of resilient arms each having a free end.
Inventor(s):	Steenfeldt-Jensen; S.o slashed.ren (Hornb.ae butted.k, DK), Hansen; Steffen (Hiller.o slashed.d, DK)
Assignee:	Novo Nordisk A/S (Bagsvaerd, DK)
Filing Date:	Oct 28, 1999
Application Number:	09/429,677
Claims:	1. A medication delivery pen comprising: a housing having proximal and distal ends and including a holder for containing a cartridge containing a medication to be delivered through a conduit connected to the cartridge, a piston rod having a not circular cross-section and an outer thread, and a piston rod drive for driving said piston rod in a distal direction inside the cartridge, said piston rod drive including a first part rotatably mounted within said housing and mating with the not circular cross-section of said piston rod, and a second part integral with said housing and having an internal thread mating the thread of said piston rod to form a self-locking thread connection, wherein rotation of said first part in a first direction relative to said second part drives said piston rod in a distal direction; and a one-way coupling comprising: a) an annular ring of equally spaced internal ratchet notches situated on the inside of said housing, which internal notches have a steep front edge and a ramp shaped trailing edge, b) a pawl surrounding said piston rod and having at least a pair of resilient arms, each arm having a free end, said pawl being connected with said first part of said piston rod drive, and c) means situated on said free end of each arm for engaging in the internal ratchet notches of said annular ring, which means abuts said steep front edge of said internal notches, thereby preventing said pawl body from rotating in one direction relatively to said housing, the prevented direction being one by which the piston rod would be transported in a proximal direction. 2. A medication delivery pen according to claim 1, wherein said two or more arms are disposed with the same relative spacing around the circumference of said pawl. 3. A medication delivery pen according to claim 1, wherein said steep front edges of said internal notches on opposite sides of said annular ring are parallel to each other. 4. A medication delivery pen according to claim 1, wherein said arms extend circumferentially from a body portion of said pawl and wherein said means situated on said free end of each arm is the end-surface of the arm lying circumferentially opposite said pawl and abutting said steep front edge of said internal notches. 5. A medication delivery pen according to claim 1, wherein said arms extend circumferentially from said pawl body and wherein said means situated on said free end of each arm includes a protrusion. 6. A medication delivery pen comprising: a housing having proximal and distal ends and including a holder for containing a cartridge containing a medication to be delivered through a conduit connected to said cartridge, a piston rod having a not circular cross-section and an outer thread, and a piston rod drive for driving said piston rod in a distal direction inside the cartridge, said piston rod drive including a first part having an internal thread mating the thread of said piston rod to form a self-locking thread connection, and a second part integral with said housing and mating with the not circular cross-section of said piston rod, wherein rotation of said first part in a first direction relative to said second part drives the piston rod in a distal direction; and a one-way coupling comprising: a) an annular ring of equally spaced internal ratchet notches situated on the inside of said housing, which internal notches have a steep front edge and a ramp shaped trailing edge, b) a pawl surrounding said piston rod and having at least a pair of resilient arms, each arm having a free end, said pawl being connected with said first part of said piston rod drive, and c) means situated on said free end of each arm for engaging in the internal ratchet notches of said annular ring, which means abuts said steep front edge of the internal notches, thereby preventing said pawl body from rotating in one direction relatively to said housing, the prevented direction being one by which the piston rod would be transported in a proximal direction. 7. A medication delivery pen according to claim 6, wherein said two or more arms are disposed with the same relative spacing around the circumference of said pawl. 8. A medication delivery pen according to claim 6, wherein said steep front edges of said internal notches on opposite sides of said annular ring are parallel to each other. 9. A medication delivery pen according to claim 6, wherein said arms extend circumferentially from a body portion of said pawl and wherein said means situated on said free end of each arm is the end-surface of the arm lying circumferentially opposite said pawl and abutting said steep front edges of said internal notches. 10. A medication delivery pen according to claim 6, wherein said arms extends circumferentially from said pawl body and wherein said means situated on said free end of each arm includes a protrusion. 11. A medication delivery pen comprising: a housing having proximal and distal ends and including a holder for containing a cartridge containing a medication to be delivered through a conduit connected to said cartridge, a piston rod having a not circular cross-section and an outer thread, and a piston rod drive for driving said piston rod in a distal direction inside the cartridge, said piston rod drive including a first part having an internal thread mating the thread of said piston rod to form a self-locking thread connection, a second part mating with the not circular cross-section of said piston rod, wherein said first and second parts are rotatable relative to one another to drive the piston rod in an axial direction; and a one-way coupling comprising: a) an annular ring member of equally spaced internal ratchet notches, and b) a pawl member having at least a pair of resilient arms, each arm having a free end for engaging said ratchet notches so as to allow rotation between said ring and said pawl in a first rotational direction and prevent rotation between said ring and said pawl in a second rotational direction, wherein said members are coupled between said housing and said piston rod drive such that rotation between said members in said first rotational direction causes the piston rod to move in a distal direction, and such that said members prevent movement of said piston rod in said proximal direction.