Multiple dosage injector with rack and pinion dosage system

A dispensing mechanism, comprising:

• a housing having a proximal-distal axis;
• a ram within the housing, movable in a distal direction relative to the housing;
• a push button moveable along the proximal-distal axis relative to the housing, the push button including a push button slot at a distal portion of the push button;
• a crank arm having a pawl tooth, a pivot point, and a crank arm engagement member slideably engageable with the push button slot such that movement of the push button causes the crank arm engagement member to move along the push button slot, causing rotation of the crank arm about the pivot point;
• and
• a ratchet gear having a first set of teeth releasably engageable with the pawl tooth and a second set of teeth releasably engageable with the ram,
• wherein engagement of the pawl tooth with the first set of teeth of the ratchet gear causes the ratchet gear to rotate, causing the ram to distally advance relative to the housing, and
• wherein the ram includes a lockout protrusion and the push button includes a lockout aperture, the lockout aperture engaging with the lockout protrusion in a locked position.