Autobalance roping and drive arrangement
View Patent ↗An autobalancing roping and drive arrangement for elevators which continuously balances the weight of an elevator cab and the weight of a counterweight such that the force on the drive motor necessary to move the cab from floor to floor is minimized. A weighting device connected to a drive sheave imparts a downward force on the drive sheave and creates a tension in a force section, causing traction contact between the drive sheave and the drive rope. The tension in the force section includes a downward vertical component of force. This component and the weight of the counterweight combine to create a downward force on one side of the suspension sheave section. The downward force balances the downward force created by the weight of the cab on the opposite side of the suspension sheave section. The tension in the force section automatically compensates for the difference in weight between the cab and the counterweight and thereby maintains the elevator in balance.
1. A traction drive elevator having an autobalancing roping and drive arrangement comprising:
a vertically displaceable elevator cab;
a vertically displaceable counterweight;
a suspension sheave section located above the cab and counterweight;
a suspension rope passing over and guided by the suspension sheave section, the suspension rope having a first end attached to the counterweight on one side of the suspension sheave section and having a second end attached to the cab on the opposite side of the suspension sheave section;
a drive sheave located below the cab and the counterweight;
a drive rope passing under and in traction contact with the drive sheave, the drive rope having a first end attached to the counterweight and having a second end attached to the cab, the length of drive rope between the drive sheave and counterweight defining a force section, the traction contact between the drive sheave and the drive rope for driving the drive rope and vertically displacing the cab and counterweight;
a weighting device connected to the drive sheave and imparting a force on the drive sheave and creating a tension in the force section that includes a downward vertical component of force;
wherein said weighting device comprises a lever arm which is moved downward by a variable force, the variable force causing the weight of the cab and the weight of the counterweight to be equalized such that the amount of force necessary to move the car between landings is minimized, said variable force being generated by a weight which slides along the length of the lever arm;
the downward vertical component of force in the force section and the weight of the counterweight combining to create a downward vertical force in the suspension rope on one side of the suspension sheave section to balance the downward force created by the weight of the cab on the opposite side of the sheave section.
2. The traction drive elevator according to claim 1 , wherein the downward vertical component offeree generated by the tension in the force section varies from zero lbs to 5,000 lbs.
3. The traction drive elevator according to claim 1 , further comprising a tensioning device for tensioning the drive rope and removing slack therefrom.
4. The traction drive elevator according to claim 1 , wherein the suspension sheave section is composed of one or more suspension sheaves.
5. The traction drive elevator according to claim 1 , further comprising a deflector sheave located below the cab.
6. The traction drive elevator according to claim 1 , wherein the suspension rope, drive rope, or both, are comprised of a plurality of separate strands.
7. The traction drive elevator according to claim 1 , wherein the drive sheave is driven by a regenerative drive motor capable of regenerating energy from the kinetic and potential energy created during operation of the elevator.