A turnbuckle linkage pivoted at each end provides the means to expand a manhole riser. The construction allows efficient application of a screw. A 50-lb. force applied 6-in. from the center of the turnbuckle exerts a 4000 lb. tangential force in the riser ring. Thus, the riser ring is bent to fit the out of round worn manhole opening.
The manhole ring is forced out against the casting around the full circumference with this pivoted turnbuckle mechanism. The installation resembles a pressed in bearing. The risers are designed to be a reliable, efficient way to bring manholes up to a new grade.
The unit does not obstruct the entrance to the manhole. There are no extensions to hinder workers and equipment using the manhole. All skirts and linkage parts are cadmium plated with dichromate finish or galvanized. The pivot pins are stainless steel. The linkage, with bending or binding, contracts the ring for easy insertion, then expands the ring to fit diameter variations of ±1/2 in.
American Highway Products Ltd., P.O. Box 640, Bolivar, OH 44612. Tel: 888-272-2397; Fax: 330-874-3800.