Key Ball Cushion Ring

Vulcan always tried to be responsive to the needs of its customers. Sometimes, however, the way they wanted to do things got in the way of progress, and the Key Ball Cushion Ring was a good example of that in action.

Vulcan had used the “standard pot” to hold its cushion material from the beginning of the product line. Vulcan’s tapered cushion configuration was adapted from wood cushion blocks, and hardwood cushions were the rule for many years. As hardwood became scarcer Vulcan turned to other materials.

The deficiencies of the situation were apparent. Raymond for its part had developed the capblock shield using alternating micarta and aluminium and that became its standard by the end of the 1950’s. The cushion was durable and its energy transmission characteristics were superior to anything being put in the standard pot. Some contractors like Santa Fe used the capblock follower, but the higher stack height put off many of Vulcan’s customers, especially McDermott and Brown & Root.

In addition to these problems, the top rim of the cushion pots broke for a variety of reasons. The situation is succinctly described in Vulcan’s own literature:

In 1974 Vulcan patented an attempted solution to the problem, the Key Ball Cushion Ring. Again Vulcan’s literature describes the concept and execution, especially for new caps.

Vulcan manufactured a few of these units, but for all of the promise the Key Ball Cushion Ring the reality had one problem: the ball, being harder than the steel around it, would create a groove as the ring moved upward, and the ring would eventually come out. Part of the problem was inertial, but part of the problem was that the cushion materials used at the time would, to varying degrees, become plastic in use, flow under the ring, and jack it out of the cap.

With the failure of the Key Ball Cushion Ring, Vulcan was “back to square one” with this problem. In the 1980’s McDermott migrated to the capblock follower, which provided–and still provides–a removable ring, additionally combined with a superior cushioning system.


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