Heavy Duty Torsion Springs:
Heavy duty torsion springs are usually found in lift-gates, hatches, or lids. They are able to exert large amounts of torque when a torque load is placed on the legs. Their function in a truck's lift gate, for example, is to assist the user to support the weight of the gate safely while pulling it down. They also assist the user in lifting the gate back to its original position with minimal human force.
Heavy duty torsion springs can be custom-made to match the torque that you require and to fit your application properly. There is also a stock torsion springs catalog you may search through to find your heavy duty torsion spring.