Patent ID: 8721479

Claim:
A belt tensioning device for preventing excess tension on a spindle, comprising: a spindle aligned along, and drivable about, a spindle axis; an endless belt operatively connected to the spindle; a rotational driver aligned along a drive axis, the rotational driver also operatively connected to the endless belt and operable to drive the endless belt so as to rotatably drive the spindle; a fixed structure located adjacent the spindle and the rotational driver; a carrying structure supporting the rotational driver, including a rod extending away from the drive axis; a clutch supported on the fixed structure and operatively connected to the rod, the clutch adapted to cooperate with the rod to selectively move the drive axis towards/away from the spindle axis, thereby to loosen/tighten the endless belt, the clutch further including: a nut operatively connected to the rod; an outer shell surrounding the rod, one of the nut and the outer shell having a mounting recess and the other of the nut and the outer shell having a slot; a tensioning member that supplies a variable resisting force that resists movement of the nut and the rod relative to the structure; an engagement member having an extended state and a retracted state, the engagement member being mounted in said mounting recess and in an extended state so as to co-act with said slot, such that rotation of the outer shell in a first rotational direction causes rotation of the nut, and thereby moves the rod and the drive axis in a direction away from the spindle axis so as to tension the endless belt while the resisting force resists movement of the nut toward the spindle axis, whereby continued rotation of the outer shell in the first rotational direction continues to increase the tension of the belt so as to eventually overcome an initial resisting force, whereby the nut begins to move toward the spindle axis, and still further rotation of the outer shell causes the nut to move a sufficient distance to cause the engagement member to transition to the retracted state and to disengage from the slot, such that, thereafter, any further rotation of the outer shell in the first rotational direction causes no further rotation of the nut, and wherein subsequent rotational movement of the outer shell in a second rotational direction opposite the first rotational direction causes the engagement member to transition back to the extended state and to re-engage with the slot, thereby to cause the nut to rotate in the second rotational direction and to move the rod and the drive axis toward the spindle axis; and a rolling element thrust bearing located adjacent the tensioning member, thereby to facilitate rotational movement of the outer shell relative to the nut after the engagement member has disengaged from the slot.