Mobile-equipment designers know that in the real world they have to deal with more than level surfaces and two-dimensional access envelopes. Designers at JLG Industries in McConnellsburg, Pennsylvania, know that additional obstacles at ceiling level will challenge the platform on their boom lifts. That’s why they created the Model E300AJP electric boom lifts with the exclusive Jib-PLUS boom that provides access up, over, and around obstacles 30 feet above the floor.
Eight 6-V/370-Ahr batteries power the 15,000-pound boom lift through a 48-V DC electrical system. Dual electric traction motors, with automatic spring-applied multiple disc brakes, handle travel. Wheel sensors feed information back to the travel control to ensure that both wheels work independently for improved traction on uneven surfaces or while driving over obstacles.
A permanent-magnet motor drives a highly efficient, internal crescent-gear pump to supply all the hydraulic functions from a three-gallon reservoir. The motor is energized to run the pump only when flow is needed, thus maximizing time between battery charges.
The control console on the 30 x 48-inch operator’s platform incorporates 12-V switches that energize solenoid-actuated, pressure compensated cartridge valves in the operating circuits down at the chassis. A minimum number of controls are used, and they are organized on the console to enhance the operator interface. High-contrast graphics and easy-to-understand symbols make the controls operator-friendly and help to shorten training time.
Reach specifications for the Model E300AJP include 20 feet, six inches horizontally; 13 feet, 1 inch of up-and-over height; and 360° of non-continuous rotation. The articulated jib produces a near-vertical orientation as it swings through a range from 55° downward to 86° upward. A Parker Helac rotary actuator at the base of the Jib-PLUS adds a 140° arc of side-to-side movement to the jib and platform. Finally, the 500-pound capacity platform is rotated 180° by a second Helac rotary actuator. In other words, the E300AJP offers truly versatile positioning.
Parker builds both of the Helac rotary actuators installed at the boom’s working end. The Helac L20-15 actuator between the main and jib booms is an integral part of the boom structure — functioning as a mounting bracket, bearing support, and power hinge, as well as the rotational device. The main boom is pinned to the upper hole in the actuator's clevis; the leveling cylinder is pinned to the lower hole. The jib-boom assembly mounts right on the actuator. Its upper mounting bracket is bolted to the large diameter, drilled and-tapped shaft flange. The jib’s lower mounting bracket is attached to the bottom of the actuator by a tie rod that passes through the actuator's shaft bore. (The tie rod functions as a second load path, for added safety.) The straddle orientation of the jib boom not only contributes stability and rigidity but also results in an exceptional 65,000 inch-pounds moment-load capacity (a 2.75:1 design margin).
The heavy load-carrying ability is largely due to Helac's patented integral journaled bearing design, which eliminates any need for external bearing support. Helac rotary actuators use a sliding-helical-gear operating concept that produces high torque from a compact envelope. (The Model L20 15 is rated for 15,000 inch-pounds at 3,000 psi.) High torque output combines with zero leakage for smooth operation with a solid feel and permits selected positions to be held without drift. For extra safety on the E300AJP. The hydraulic circuit includes an integral, factory installed counterbalance valve in a protected position between the clevises.
This article was contributed by Daniel Morgado, applications engineer, Helac Business Unit, Cylinder Division and was originally published by Hydraulics & Pneumatics.