Drive shaft assembly for driven accessory devices

A method for selectively coupling a prime mover device to an accessory device, the method comprising:

• providing a drive shaft assembly that includes an outer shaft, an inner shaft, and an interface medium, wherein the outer shaft defines a central channel, wherein the inner shaft extends into the central channel of the outer shaft and defines a clearance gap between an interior surface of the outer shaft and an exterior surface of the inner shaft, wherein the interface medium is disposed in the clearance gap and configured to rotationally couple the outer shaft and the inner shaft in an operational state of the drive shaft assembly, and wherein said providing the drive shaft assembly includes forming the outer shaft to include one or more cavities that are open to the clearance gap and extend radially outward from the clearance gap to respective base surfaces of the one or more cavities;
• mechanically coupling one of the inner shaft or the outer shaft to the prime mover device;
• and
• mechanically coupling the other of the inner shaft or the outer shaft to the accessory device, wherein, in the operational state, rotational torque exerted by the prime mover device is transmitted via the drive shaft assembly to the accessory device,
• wherein, in response to a temperature of the drive shaft assembly exceeding a threshold temperature, the interface medium is configured to at least partially melt and rotationally uncouple the outer shaft and the inner shaft, such that the drive shaft assembly no longer transmits the rotational torque to the accessory device, in a fault state of the drive shaft assembly, and wherein at least a portion of the interface medium flows from the clearance gap into the one or more cavities in the fault state and is contained within the one or more cavities.

An engine drive system comprising:

• a fuel combustion engine including a gear box;
• an accessory device;
• and
• a drive shaft assembly comprising:
• an outer shaft that defines a central channel therethrough, wherein the outer shaft is mechanically connected to one of the gear box or the accessory device;
• an inner shaft extending into the central channel of the outer shaft and defining a clearance gap between an interior surface of the outer shaft and an exterior surface of the inner shaft, wherein the inner shaft is mechanically connected to the other of the gear box or the accessory device, and wherein the outer shaft includes cavities that are open to the clearance gap and extend radially outward from the clearance gap to respective base surfaces of the cavities;
• and
• an interface medium disposed in the clearance gap and configured to rotationally couple the outer shaft and the inner shaft in an operational state of the drive shaft assembly,
• wherein in response to a temperature of the drive shaft assembly exceeding a threshold temperature, at least a portion of the interface medium is configured to flow from the clearance gap into the cavities, which rotationally uncouples the outer shaft and the inner shaft in a fault state of the drive shaft assembly.