Concrete utility poles have found their place in precast concrete mass production, and their market share is growing. Technologies that would help produce them better, faster, and less expensively would meet the increasing demands of engineers.
Graeme Reginald Hume of Werribee, Australia, received a
U.S. patent for his "Rapid Moulding of Long Concrete Poles." Assigned to what ostensibly is his company, Hume Brothers Pty Ltd.—also of Werribee—the invention is aimed at producing precast concrete power transmission poles of higher quality and durability at lower costs.
The poles are formed vertically with a cored center, which is nothing unique. However, the forms are innovative. The inner surface of the form and the outer surface of the core are covered with a "liner" that is essentially a balloon of sorts. The core is inserted into the form, and both liners are inflated with either pneumatic or hydraulic pressure.
Then the upper end of the form cavity is sealed with a cap, and concrete is pumped into the cavity from the bottom through a filler elbow. About halfway up the length of the form, a set of pressure sensors is installed. When the pressure inside of the form cavity reaches a predetermined level—indicating that the cavity is filled to the desired pressure—the sensors send signals to a controller that shuts off the pump.
Another automation feature is an end cap on the top of the form cavity that is equipped with an actuating cylinder. The cap has another sensor designed to sense the complete filling of the cavity. It seems that it's designed to add a level of safety for avoiding an overfill in the event that one or both of the mid-cavity sensors fails.
Regulating the pressure reduction simultaneously between the core liner and the form liner eliminates the possibility of a pressure differential occurring across the cross-section of the pole and causing damage to it. This eliminates the potential for abrasion to the surfaces of the pole during extraction.