An injection device is provided having a housing with a plunger stop block and a cartridge assembly for holding a fluid. The cartridge assembly has a plunger that has an injection needle. A main spring assembly having a main spring and a plate having first and second support arms is positioned in the housing. A release component is positioned in the housing and includes a release ring having teeth with sliding surfaces, and the release ring defines first and second release slots. An actuator having an actuator ring from which actuator rods extend is positioned in the housing. The actuator rods can engage the sliding surfaces of the teeth, such that when a force is applied to the actuator ring the release component rotates and releases the main spring, and this causes the plunger to contact the plunger stop block and drive fluid out of the injection needle.