A pulley unit has a hub configured to be connected to a crankshaft, a pulley coaxial to the hub and supported in a rotationally free manner with respect thereto, a clutch interposed between the hub and the pulley, and an actuator for controlling the clutch, The clutch has an inner disc rotationally coupled to the hub and an engagement portion housed inside the pulley, a mobile member axially movable between an engagement position in which the mobile member rotationally couples the pulley to the engagement portion of the inner disc and a disengagement position in which the pulley is rotationally free with respect to the inner disc, and an elastic element acting on the mobile member to push it towards the engagement position.

A pulley unit has a hub configured to be connected to a crankshaft, a pulley coaxial to the hub and supported in a rotationally free manner with respect thereto, a clutch interposed between the hub and the pulley, and an actuator for controlling the clutch, The clutch has an inner disc rotationally coupled to the hub and an engagement portion housed inside the pulley, a mobile member axially movable between an engagement position in which the mobile member rotationally couples the pulley to the engagement portion of the inner disc and a disengagement position in which the pulley is rotationally free with respect to the inner disc, and an elastic element acting on the mobile member to push it towards the engagement position.

A clutch system includes a rotary input member, a wrap spring clutch and a rotary output member. The wrap spring clutch has a first end, a second end, and a plurality of coils. The stiffness of the wrap spring clutch is selected such that, when transmitting less than a selected coil engagement torque, the clutch system transmits torque helically from the rotary input member, to the second end, helically through the wrap spring clutch to the first end, and into the rotary output member. When transmitting more than the selected coil engagement torque, the clutch system transmits torque in parallel from the rotary input member, to the second end, helically through the wrap spring clutch to the first end, and into the rotary output member, and from the rotary input member through the coil engagement surface, to the first end, and into the rotary output member.

A clutch system includes a rotary input member, a wrap spring clutch and a rotary output member. The wrap spring clutch has a first end, a second end, and a plurality of coils. The stiffness of the wrap spring clutch is selected such that, when transmitting less than a selected coil engagement torque, the clutch system transmits torque helically from the rotary input member, to the second end, helically through the wrap spring clutch to the first end, and into the rotary output member. When transmitting more than the selected coil engagement torque, the clutch system transmits torque in parallel from the rotary input member, to the second end, helically through the wrap spring clutch to the first end, and into the rotary output member, and from the rotary input member through the coil engagement surface, to the first end, and into the rotary output member.

The present disclosure describes a wrap spring torque nipple that includes a first helical spring, a second helical spring, and a middle portion connected to and between the first helical spring and the second helical spring. The first helical spring and the second helical spring have different rotational helix orientations, and the first helical spring is configured to receive an input shaft and the second helical spring is configured to receive an output shaft, wherein the wrap spring transfers rotational power up to a defined torsional value from the input shaft to the output shaft.

The present disclosure describes a wrap spring torque nipple that includes a first helical spring, a second helical spring, and a middle portion connected to and between the first helical spring and the second helical spring. The first helical spring and the second helical spring have different rotational helix orientations, and the first helical spring is configured to receive an input shaft and the second helical spring is configured to receive an output shaft, wherein the wrap spring transfers rotational power up to a defined torsional value from the input shaft to the output shaft.

Clutch assemblies that can provide variable break-away torques are described. An exemplary multi-state clutch assembly can include a shaft, a first frictional element frictionally engaged with the shaft and a second frictional element that can provide variable friction. When the second frictional element provides a low friction, second frictional element can be rotatable relative to the first frictional element, which can remain stationary relative to the shaft. When the second frictional element provides a high friction, it can be secured to the first frictional element. Hence, the first and second frictional elements can be locked together and be rotatable relative to the shaft. Tightening or loosening the second frictional element can vary the overall break-away torque provided by the clutch assembly. The multi-state clutch assembly can be in communication with a sensor or a switch that can respond to a user to change the friction of the clutch assembly.

The present disclosure describes a wrap spring torque nipple that includes a first helical spring, a second helical spring, and a middle portion connected to and between the first helical spring and the second helical spring. The first helical spring and the second helical spring have different rotational helix orientations, and the first helical spring is configured to receive an input shaft and the second helical spring is configured to receive an output shaft, wherein the wrap spring transfers rotational power up to a defined torsional value from the input shaft to the output shaft.

The present disclosure describes a wrap spring torque nipple that includes a first helical spring, a second helical spring, and a middle portion connected to and between the first helical spring and the second helical spring. The first helical spring and the second helical spring have different rotational helix orientations, and the first helical spring is configured to receive an input shaft and the second helical spring is configured to receive an output shaft, wherein the wrap spring transfers rotational power up to a defined torsional value from the input shaft to the output shaft.

In an aspect, a clutched device is provided, including a hub, a pulley and a hub drive clutch. The hub defines an axis and is connectable to a rotatable shaft of a rotary device. The pulley is rotatable relative to the hub and is engageable with an endless drive member. The hub drive clutch is a wrap spring clutch and is controllable to operatively connect the pulley to the hub for driving the hub in a first rotational direction. An isolation spring is provided and operatively connects the hub to the pulley when the hub drives the pulley in the first rotational direction. Optionally, a pulley overrun clutch is provided and permits the pulley to overrun the hub in the first rotational direction.