Viscous rotational speed control device

A rotational speed control device comprising:

• a housing containing a viscous fluid;
• a shaft disposed in the housing and rotatable relative to the housing;
• a hub assembly secured to the shaft for rotation with the shaft;
• a rotor coupled with the shaft by way of the hub assembly, wherein the rotor rotates with the shaft until a force on the rotor due to an increase in shearing of the viscous fluid exceeds a friction force between the rotor and the hub assembly, resulting in rotation of the shaft and the hub assembly relative to the rotor;
• a spring disposed in the housing and acting on the rotor, the spring biasing the rotor axially on the shaft in a low torque direction,
• wherein a braking torque between the rotor and the housing is varied according to an axial position of the rotor on the shaft;
• a ramped ball groove member secured to the shaft for rotation with the shaft, the ramped ball groove member including a first ramped ball groove, wherein the rotor comprises a second ramped ball groove disposed in a cooperable facing relationship with the first ramped ball groove;
• and
• at least one ball positioned between the first ramped ball groove and the second ramped ball groove, wherein the ramped ball groove member and the rotor are configured such that rotation of the shaft and the ramped ball groove member relative to the rotor effects axial displacement of the rotor on the shaft by displacement of the first ramped ball groove relative to the second ramped ball groove.

A rotational speed control device comprising:

• a housing containing a viscous fluid, the housing including braking surfaces on an internal wall;
• a shaft disposed in the housing and rotatable relative to the housing;
• a hub member secured to the shaft for rotation with the shaft, the hub member including hub threads;
• a rotor coupled with the shaft by way of the hub member, the rotor including a thread segment frictionally engaging the hub threads, wherein the rotor rotates with the shaft until a force on the rotor due to an increase in shearing of the viscous fluid exceeds a friction force between the rotor and the hub member, resulting in rotation of the shaft relative to the rotor;
• and
• a spring disposed in the housing and acting on the rotor, the spring biasing the rotor axially on the shaft in a low torque direction,
• wherein a braking torque between the rotor and the housing is varied according to an axial position of the rotor on the shaft.

A rotational speed control device comprising:

• a housing containing a viscous fluid;
• a shaft disposed in the housing and rotatable relative to the housing;
• a hub assembly secured to the shaft for rotation with the shaft;
• a rotor coupled with the shaft by a frictional engagement with the hub assembly;
• and
• a spring disposed in the housing and acting on the rotor, the spring biasing the rotor axially on the shaft in a low torque direction,
• wherein a braking torque between the rotor and the housing is varied according to an axial position of the rotor on the shaft, wherein the housing comprises braking surfaces on an internal wall, wherein the braking torque is dependent on a position of the rotor relative to the braking surfaces, wherein the hub assembly comprises a hub member having hub threads, and wherein the rotor comprises a thread segment frictionally engaging the hub threads.

A rotational speed control device comprising:

• a housing containing a viscous fluid;
• a shaft disposed in the housing and rotatable relative to the housing;
• a hub assembly secured to the shaft for rotation with the shaft;
• a rotor coupled with the shaft by a frictional engagement with the hub assembly;
• a spring disposed in the housing and acting on the rotor, the spring biasing the rotor axially on the shaft in a low torque direction,
• wherein a braking torque between the rotor and the housing is varied according to an axial position of the rotor on the shaft;
• and
• a ramp assembly cooperable with the shaft and the rotor, wherein the axial position of the rotor on the shaft is varied by the ramp assembly according to the braking torque between the rotor and the housing, wherein the ramp assembly comprises:
• a ramped ball groove member secured to the shaft for rotation with the shaft, the ramped ball groove member including a first ramped ball groove,
• a second ramped ball groove formed in the rotor and disposed in a cooperable facing relationship with the first ramped ball groove;
• and
• at least one ball positioned between the first ramped ball groove and the second ramped ball groove, wherein the ramped ball groove member and the rotor are configured such that rotation of the shaft and the ramped ball groove member relative to the rotor effects axial displacement of the rotor on the shaft by displacement of the first ramped ball groove relative to the second ramped ball groove.