Medical device with means to improve transmission of torque along a rotational drive shaft

A catheter device for insertion into bodily lumens or cavities, comprising:

• an elongate hollow sheath having a distal end portion, a proximal end portion, and an elongate midsection;
• a rotational drive shaft housed within said elongate hollow sheath;
• a functional element mounted to said rotational drive shaft at a location that is remote from said proximal end portion of said elongate hollow sheath;
• and
• at least one frictional component operatively associated with at least one of said rotational drive shaft and said functional element, such that said frictional component bears radially outwards to be in frictional contact with an inner surface of said elongate hollow sheath;
• said frictional component being configured such that an amount of frictional force produced by contact between said frictional component and said inner surface of said elongate hollow sheath is uniform regardless of the angular orientation and longitudinal translation of the rotating components within said hollow elongate sheath;
• said frictional component being configured such that the contact between said frictional component and said inner surface of said elongate hollow sheath is independent of the angular orientation and longitudinal translation of the rotating components within said hollow elongate sheath;
• and
• such that during rotation of said functional element by said rotational drive shaft, said rotational drive shaft is configured to operate with a higher torsional load than in an absence of said frictional component, thereby reducing non-uniform rotational distortion as said functional element rotates inside said elongate hollow sheath.