Complex sentence: As the flat spring moves downward the upward force of the curved spring reduces causing the motion to accelerate even in the absence of further motion of the actuator until the flat spring impacts the normally-open contact.
Split into simpler sentences: As the flat spring moves downward, the upward force of the curved spring reduces, causing the motion to accelerate even in the absence of further motion of the actuator. This continues until the flat spring impacts the normally-open contact.