Engineers at Intralox L.C.C, Harahan, La., used electric actuators to improve the speed and precision of a palletizing unit that takes variously sized products from a conveyor, and lines them up and orients them to form layers on shipping pallets.
Pneumatic cylinders lacked the flexibility to quickly deal with packages of different sizes and shapes. And earlier electric actuators couldn’t handle washdowns common in the food and beverage industries. Intralox eventually teamed with Tolomatic, Hamel, Minn., to devise a totally enclosed ball-screw actuator the company calls an ERD actuator.
The palletizer uses actuated roller belts that move containers linearly while also moving them left or right, spinning them around, and sorting them to specific locations in a pallet layer. The conveyor belt uses the new actuators beneath various zones and they activate the pinions controlling the longitudinal rollers that make up the moving belt. The pinions make the rollers spin left or right.
As packages pass over a diversion zone, for example, the rollers move packages sideways by a predefined amount as they also travel forward down the belt. Any given 10-ft section of the roller belt contains eight to 16 actuators, depending on the complexity of what it can do to packages. With this configuration, packages can be nudged a few degrees right or left, or make a complete 90° turn as they move along the belt.
In the redesigned palletizer, a high-torque stepper motor drives ERD actuators through couplings designed by Tolomatic to stand up to harsh use. Each actuator only moves forward or back 6 mm each time it activates a pinion, and the actuator stroke only lasts 50 msec. But with a conveyor moving 250 packages/min, actuators move four times per second. “This represents only a 25% duty cycle,” says David Marsh, Intralox senior electrical controls engineer. “But it’s a lot of movement, force, and action for a ball screw.”
The ball-screw actuator can exert up to 500 lb of force, sits in a rugged 304-stainless-steel housing, and has stroke lengths adjustable up to 24 in. It can also be outfitted to qualify for up to an IP67 rating.