A controller assembly of a fluid delivery apparatus includes a body component and a plunger component slidably coupled to the body component. The plunger is positionable between a first position in which the plunger is nearest to the body component, and a second position in which the plunger component is furthest from the body component. A bias assembly positioned between the body component and the plunger component applies a two stage force profile to the plunger component. The bias assembly includes a first and a second biasing member. In the first position, the first and second biasing members apply first and second forces profiles, respectively, to the plunger component. In the second position, the first biasing member is prevented from applying the first force profile to the plunger component, and the second biasing member applies the second force profile to the plunger component.
