Martin Engineering Impact Cradles

Martin Engineering offers a family of impact cradles engineered to prevent belt and mainframe damage and eliminate spillage of heavy materials. The Martin Impact Cradles Heavy Duty (HD), Medium Duty (MD) and Light Duty (LD) feature a bed of steel angles lined by energy-absorbing impact bars with a top layer of low friction, ultra-high molecular weight (UHMW) plastic. The result is longer lasting conveyor belts and components, with less fugitive material and a safer work area.PTP ImpactCradle 400

“Fine material discharged from a height can have just as much force as a coarse load,” explained Product Engineer Daniel Marshall. “Without proper impact absorption and distribution, all of that force is exerted on the belt, essentially crushing it against a rigid surface underneath. The impact beds absorb the energy, so the belt doesn’t have to. It also creates a flat edge for the apron seal, to prevent spillage and fugitive dust.”

The Martin Engineering cradles are designed to be located at transfer points of receiving conveyors, under the hopper and chute box, close to the tail pulley. Depending on the force of the discharged material, they can possess different structural qualities. All three Martin Impact Cradles feature wing supports, which adjust to match CEMA standard trough angles, as well as a 5 percent fine-tuning adjustment angle. This allows for the cradle to accommodate the idler profiles of different manufacturers and assure a tight belt seal.

The Martin Impact Cradle HD is the company’s most rugged design, able to withstand impact forces from 12,000 to 17,000 lbf. (53.4 to 75.6 kN) and drop heights of light material up to 50 ft. (15.2 m). Classified as Heavy-Duty (H) in CEMA Standard 575-2000, it fits E-6 and E-7 conveyor configurations. Support beams in the center of the cradle are set 3/4 in. (19 mm) below the receiving belt’s line of travel, allowing the belt to avoid sustained friction when running empty, yet absorbing significant impacts during loading while still retaining a tight seal.

“The HD Cradle is designed to handle a load equal to a full-sized refrigerator being dropped from a height of 10 ft.,” said Marshall.

The unit is equipped with 7-13 heavy-duty impact bars, depending on width. Installed perpendicular to the belt path, the bars are reinforced by a steel support structure with a base of impact-absorbing 50-durometer styrene-butadiene (SBR) rubber and a top layer of slick UHMW plastic. They are engineered to withstand dynamic energy and a heat range of -20° to 140°F (-29° to 60°C) without compromising the structural integrity of the conveyor frame. The cradle is on a Trac-Mount, allowing it to slide out for easy bar replacement.

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