1442584-A is referenced by 11 patents.
1442584 Elevation propelling arrangements JOHNS & WAYGOOD Ltd 4 Feb 1975 [5 April 1974] 4643/75 Heading B8L A traction drive system for an elevator comprises head and foot sheaves 1, 4 located in an elevator shaft, a rope 8 attached at one end 9 to an elevator car 3 and arranged to pass in turn over a floating sheave 2 mounted in a sheave frame 5 on the car, and over the foot and head sheaves, the other end of the rope 8 being attached to the frame 5, and means to apply drive to the rope 8 through either the head or foot sheave 2,4, or through a separate traction sheave, Fig. 3 (not shown), over which the rope passes. The frame 5 is slideably mounted in guides 6 on top of the car 3 and is biased upwardly by a spring 7.; As shown, the head sheave 1 is the traction sheave, and the tension in the rope 8 between its point of attachment 9 to the car 3 and the point where it reaches the traction sheave 1 is equal to the weight of the car plus its load, ignoring the rope weight. The tension in the rope between the traction sheave 1 and the point of attachment to the frame 5 is twice the tension in the remaining part of the rope. As the car is loaded, the tension in the rope and therefore the available tractive force, is automatically increased. If the car 3 bottoms on a buffer 11 in the shaft, the tension in the rope is relieved, but the spring 7 extends to lightly tension the rope through the sheave 2 whereby a low tractive force is possible from the sheave 1 until the weight of the car again applies tension to the rope.; If the car 3 engages an overrunning stop 10 at the shaft top, the rope tension be-. tween the frame 5 and the traction sheave 1 will momentarily increase with consequent decrease in the rope tension between the traction sheave and the attachment point 9 on the car, whereupon the tractor motor will either slip or stall depending on its available power output.