Auto-injector
An injection device comprising a housing to house a syringe, an activation member, a drive mechanism to, upon activation by the activation member, drive a plunger driver between a first position and a second position to operate the syringe within the housing and a damping mechanism configured to damp movement of the plunger driver in either a forward motion or a rearward motion. The plunger position may affect an amount of travel of the plunger driver before it is in contact with the plunger and the plunger is in contact with a drug within a barrel. During travel, a drive force may cause rapid acceleration of the plunger driver, and damage to the syringe or discomfort to an injection recipient when contact between the plunger driver, the syringe, and the recipient is made. Damping of the forward motion of the plunger driver reduces or overcomes the risk of this.
1 . An injection device comprising:
a. a housing configured to house a syringe;
b. an activation member;
c. a drive mechanism configured to, upon activation by the activation member, drive a plunger driver between a first, initial, position and a second, final, position thereby to operate the syringe within the housing;
d. a damping mechanism configured to damp movement of the plunger driver in a forward motion and a rearward motion,
wherein the damping mechanism comprises an arrangement which comprises a rack and a pinion, wherein the pinion is coupled to the plunger driver and the rack is fixedly coupled to the housing in an axial direction at all times during operation of the injection device, and
wherein the rack and the pinion are configured to damp the forward motion and the rearward motion of the plunger driver.
2 . The injection device as claimed in claim 1 , wherein the damping mechanism is configured to damp an initial portion of the forward motion of the plunger driver.
3 . The injection device as claimed in claim 1 , wherein the damping mechanism is configured to damp the forward motion of the plunger driver from the first, initial, position to the second, final, position.
4 . The injection device according to claim 1 , wherein the rack extends along a portion of the housing at and/or adjacent to the plunger driver when the plunger driver is in the first, initial, position thereby to damp an initial portion of the forward motion of the plunger driver.
5 . The injection device according to claim 1 , wherein the rack extends along a portion of the housing at and/or adjacent to the plunger driver when the plunger driver is in the second, final, position thereby to damp a final portion of the forward motion of the plunger driver.
6 . The injection device according to claim 1 , wherein the rack extends between a location of the plunger driver in the first, initial, position and a location of the plunger driver in the second, final, position thereby to damp a full region of the forward motion or the rearward motion of the plunger driver after the activation.
7 . The injection device as claimed in claim 1 , wherein the housing is further configured to house the activation member, the drive mechanism, the plunger driver, and the damping mechanism.