Safety centering basket for borehole casings - in e.g. mines and oil-fields, incorporates flat springs securely held in steel rings, but exchangeable

摘要

Basket for centering tubes forming casings in shafts in oil-fields is composed of flat steel springs inserted at their ends in enlarged parts of a steel ring formed of two hinged half-rings. The springs are held by bars on the steel ring. The bars extend from the enlarge parts and are bent inwards. The enlarge parts have mouldings which bear on lateral grooves provided in the flat steel springs. The ends of the bars are forced through grooves so that they bear on the outer surface of the steel ring, holding the bars and preventing them from coming out of the enlarged parts of the rings. Problems associated with existing centering baskets are avoided. The form of the springs according to the invention gives firm positioning and an economy of 30% in the material of the springs, the shearing forces being distributed over a large surface.