Multi-piston activation mechanism

An actuator assembly of a downhole tool, the actuator assembly comprising:

• a plurality of pistons;
• a low pressure chamber defined at least in part by the plurality of pistons and an inner surface of the downhole tool;
• a first high pressure chamber defined at least in part by the plurality of pistons and the inner surface of the downhole tool;
• a second high pressure chamber defined at least in part by the plurality of pistons and the inner surface of the downhole tool;
• and
• a restrictor apparatus positioned adjacent a first end of the actuator assembly, the restrictor apparatus including a low pressure pathway within which a restrictor device is positioned, and a high pressure pathway within which a check valve is positioned,
• wherein the low pressure pathway is in fluid communication with the low pressure chamber,
• wherein the high pressure pathway is in fluid communication with the first high pressure chamber and the second high pressure chamber, and wherein the check valve is a one-way check valve for allowing a pressure signal from a surface of a wellbore to pass through the check valve into the first and second high pressure chambers and for preventing an amount of pressure from flowing from the first and second high pressure chambers through the check valve in an opposite direction.

A method of actuating a tool positioned downhole in a wellbore, the method comprising:

• applying a pressure signal from a surface of the wellbore;
• passing an amount of pressure of the pressure signal through a restrictor bulkhead into a low pressure chamber;
• passing an amount of pressure of the pressure signal through the restrictor bulkhead into a first high pressure chamber;
• passing an amount of pressure of the pressure signal through the restrictor bulkhead into a second high pressure chamber;
• and
• moving a primary piston in a first direction a predetermined amount to actuate an actuator piston in response to the pressure signal from the surface of the wellbore being within a predetermined pressure window, wherein a pressure within the first high pressure chamber applies a force to a first end of the primary piston for moving the primary piston in the first direction the predetermined amount.

A downhole tool positionable within a wellbore, the downhole tool comprising:

• a housing having an outer surface that defines an inner region and an outer region of the housing;
• a primary piston positioned within the inner region of the housing for actuating an actuator piston between an open and a closed position in response to a pressure signal from a surface falling within a predetermined pressure window;
• a restrictor apparatus including a first fluid pathway in fluid communication with a low pressure chamber and a second fluid pathway in fluid communication with a first high pressure chamber and a second high pressure chamber, wherein the restrictor apparatus includes a restrictor device and a check valve for generating a pressure differential between the low pressure chamber and each of the first and second high pressure chambers;
• and
• a locking piston positioned within the inner region of the housing and coupled to a spring to exert a force in a second direction opposite a first direction, wherein the first high pressure chamber is positioned at a first end of the locking piston for applying a force to the locking piston in the first direction,
• wherein the first high pressure chamber is positioned at a first end of the primary piston for applying a force to the primary piston in the first direction for actuating the actuator piston between the open and the closed position.