Claims
- 1. A drug delivery device for dispensing set doses from a cartridge of the type containing medicine sufficient for a number of dosed injections and a piston which can be moved forward inside the cartridge to expel doses of medicine, said device comprising:a cartridge holder having open and closed positions, and into which a cartridge can be loaded when in an open position; a cartridge holder switch which generates a signal when said cartridge holder is moved from said open position to said closed position; an electrical motor; a piston rod coupled to said motor for movement responsive to activation of said motor; and an electronic circuit which receives said signal from said cartridge holder switch and activates said motor responsive to receiving said signal to move said piston rod in a first direction, towards the piston of a cartridge which has been loaded in said cartridge holder; and wherein said electronic circuit further includes a sensor to sense the power consumption of said motor and stops said motor, and thereby the movement of said piston rod in said first direction, upon detecting a predetermined increase in power consumption, indicating that the piston rod has encountered such a piston, whereby said circuit automatically sets a desired initial position of said piston rod whenever a new cartridge is loaded.
- 2. A drug delivery device as recited in claim 1, wherein said cartridge holder switch generates a cartridge holder open signal when said cartridge holder is opened and wherein, in response to said cartridge holder open signal, said electronic circuit activates said motor to move said piston rod in a direction opposite to said first direction, until reaching a predetermined retracted position.
- 3. A drug delivery device as recited in claim 2, wherein the predetermined retracted position is determined by sensing a predetermined increase in power consumption by the electrical motor.
- 4. A drug delivery device as recited in claim 3, wherein said electrical motor rotates a nut member having an inner thread mating an outer thread on said piston rod, such that said piston rod moves in a longitudinal direction when said nut member is locked against movement in said longitudinal direction and rotated.
- 5. A drum delivery device as recited in claim 4, further comprising a delivery button which is coupled to said nut member such that said delivery button moves a distance away from an original position when said nut member is rotated, which distance corresponds to the set dose.
- 6. A drug delivery device as recited in claim 5, further comprising a delivery button switch which is actuated when said button is pressed to its original position, wherein said delivery button switch is coupled to said electronic circuit such that said electronic circuit detects whether said delivery button is in said original position.
- 7. A drug delivery device as recited in claim 6, wherein said delivery button is releasably locked against movement when said delivery button is pressed to said original position.
Priority Claims (1)
Number |
Date |
Country |
Kind |
0750/96 |
Jul 1996 |
DK |
|
CROSS-REFERENCE TO APPLICATION
This application is a divisional of application Ser. No. 08/878,955 filed on Jun. 19, 1997, now U.S. Pat. No. 5,928,201 and claims priority under 35 U.S.C. 119 of Danish application serail no. 0750/96 filed Jul. 5, 1996, the contents of which are fully incorporated herein by reference.
US Referenced Citations (7)
Foreign Referenced Citations (1)
Number |
Date |
Country |
3307810 |
Sep 1983 |
DE |