Syringe with incrementally actuated plunger

Claim 1

A device for the administration of a medicament by means of a needle adapted to be inserted into the body of a person, which device comprises a cylinder (3) adapted to contain the medicament the cylinder having a bore and having a piston (5) journalled in the bore of the cylinder for axial movement in the bore towards an outlet provided with the needle or adapted to receive the needle in mounting engagement therewith, a plunger member for moving the piston (5) axially and incrementally within the bore of the cylinder (3) the plunger member (6) carrying one or more radially projecting teeth (12), an axially extending drive member (10) carrying one or more drive teeth (11) adapted to engage with the teeth (12) carried by the plunger member (6) and to move the plunger (6) axially for that distance required to discharge a single dosage of the medicament upon each actuation of the drive member (10) by a user, wherein: a. the axial spacing between axially adjacent teeth (12 or 11) on one of the plunger member (6) or the drive member (10) corresponds to the forward axial movement of the plunger member (6) required to discharge a single dose of the medicament; b. forward stop members (13) are provided which define the limits of the forward axial movement of the drive member (10) to a predetermined distance corresponding to one said tooth spacing with respect to the plunger (6), whereby forward axial movement of the drive member (10) with the teeth (11) and 12) of the drive and plunger members (10 and 6) engaged is adapted to administer said single dosage of the medicament; c. biasing means located within the cylinder and contacting the drive member (10) for biasing the drive member (10) to its axially fully retracted position at which its drive teeth (11) is/are brought into meshing register with the teeth (12) of the plunger member (6) at the start position of the forward movement of the plunger member (6); d. the drive member (10) and the plunger member (6) are mounted within the cylinder for rotation relative to one another about their longitudinal axes to bring the teeth (11 and 12) of the drive and plunger members (10 and 6) into and out of meshing engagement with each other and means are provided for preventing such relative rotation intermediate the rearward and forward extremes of travel of the drive member (10).

Claim 2

A device for the administration of a medicament by means of a needle adapted to be inserted into the body of a person, which device comprises a cylinder (3) adapted to contain the medicament the cylinder having a bore and having a piston (5) journalled in the bore of the cylinder for axial movement in the bore towards an outlet provided with the needle or adapted to receive the needle in mounting engagement therewith, a plunger member for moving the piston (5) axially and incrementally within the bore of the cylinder (3) the plunger member (6) carrying one or more radially projecting teeth (12), an axially extending drive member (10) carrying one or more drive teeth (11) adapted to engage with the teeth (12) carried by the plunger member (6) and to move the plunger (6) axially for that distance required to discharge a single dosage of the medicament upon each actuation of the drive member (10) by a user, wherein: a. the axial spacing between axially adjacent teeth (12 or 11) on one of the plunger member (6) or the drive member (10) corresponds to the forward axial movement of the plunger member (6) required to discharge a single dose of the medicament; b. forward stop members (13) are provided which define the limits of the forward axial movement of the drive member (10) to a predetermined distance corresponding to one said tooth spacing with respect to the plunger (6), whereby forward axial movement of the drive member (10) with the teeth (11) and 12) of the drive and plunger members (10 and 6) engaged is adapted to administer said single dosage of the medicament; c. biasing means located within the cylinder and contacting the drive member (10) for biasing the drive member (10) to its axially fully retracted position at which its drive teeth (11) is/are brought into meshing register with the teeth (12) of the plunger member (6) at the start position of the forward movement of the plunger member (6); d. the drive member (10) and the plunger member (6) are mounted within the cylinder for rotation relative to one another about their longitudinal axes to bring the teeth (11 and 12) of the drive and plunger members (10 and 6) into and out of meshing engagement with each other and means are provided for preventing such relative rotation intermediate the rearward and forward extremes of travel of the drive member (10).