'Floating-shaft' couplings minimize shock in inserters

Newly introduced Model SF-400 partition inserters from Wayne Automation Corp. (www.wayneautomation.com) cycle once a sec and travel 38 in. vertically. Every up/down cycle accurately inserts solid fiber or corrugated partitions into cartons that hold bottles and plastic containers ready for shipment to the marketplace.

How do these Wayne inserters maintain repeatable accuracy 24/7 at these speeds? The answer is their robust, innovative design, which uses servo motors connected to backlash-free, Zero-Max CD couplings from Zero-Max, Inc. (www.zero-max.com). These couplings damp-out shock and vibration from the inserter's vertical reciprocating and intermittent motion and maintain insertion accuracy, cycle after cycle.

"To operate without problems, conventional vertical inserters require near-perfect fiber or corrugated partitions," says Jay Bachman, vp of engineering for Wayne. "In contrast, the SF-400 inserters have designed-in features, including servo-drive systems, that help deal with less-than-perfect materials. Unlike conventional systems that rely on gravity during the insertion process, the SF-400 maintains complete insertion control from the time the partition is picked off the magazine until it is fully inserted into the case. This ensures correct partition placement into the case every cycle."

Wayne Corp. has been building innovative packaging machinery for 30 years. The company is widely known as a premier supplier of partition-handling equipment to the glass and plastic container industry. Its case-erecting equipment, for example, is backed by a guarantee to operate with a less than 0.125-percent material loss and efficiencies of 99 percent or better. With this reputation, the company strives to design its motion systems with components that will deliver with unfailing reliability.

The drive system for the SF-400 vertical-inserter mechanism is powered by an Allen-Bradley servo motor from Rockwell Automation (www.rockwellautomation.com) connected to a planetary-reduction gearbox. The motor transmits torque to the inserter via a "floating shaft," Zero-Max CD-coupling configuration connected at both ends to gearboxes. These gearboxes are connected to two timing-belt drive-pulley gearboxes.

"The combination of both intermittent and reciprocating motion at 1,000 rpm [38 in. one-way travel for every 1-sec cycle] is very demanding on the system's drive train," Bachman says. "Torque loads are a big factor in this setup with cyclical peak torques approaching sixty percent of the motor torque with vertical-load lift up to 200 pounds. We needed a coupling design that would handle these forces, and one that we could position at both ends of the two gearboxes to equalize tension on both timing belts. We chose the Zero-Max CD 6F30-AC floating-shaft coupling.

"We have confidence in CD couplings and have incorporated them in our system designs for nearly ten years because of their unique performance features and dependability. They operate very well with servo motors and have become a key design element in our systems from the time we transitioned from air-cylinder actuation to servo drives. Servo drives are energy-saving and more reliable, and require less maintenance, and the use of the CD couplings are important contributors to those benefits."

The Wayne SF-400 coupling application is unique because of the 28-in. span from one coupling's outer connecting hub to the second coupling's outer hub. Also, this setup is a real test of each coupling's patented composite-disc design integrity, which has a rated torque of 800 in. lb. With features similar to other good coupling designs, the CD coupling has one critical difference: its patented, composite-disc pack design. There's nothing else like it in the coupling world, says Zero-Max.

While the CD-coupling disc pack transmits torque like conventional couplings, it does a better job of dampening backlash and shock without coupling fatigue, which can occur in a fast-moving, high-torque system like the SF-400. The disc pack at each shaft end resists fatigue through its patented, open-arm disc design. Made of highly durable, composite material, the disc pack absorbs shock from the servo motor's intermittent motion, while maintaining a zero-backlash condition.

Also, the coupling's disc design and hub configuration provide excellent support for the floating-shaft component without imposing excessive radial loads on the connected equipment and bearings. Precision machining of the coupling components also gives the connection good dynamic balance for smooth, quiet operation.

High speed is also a key feature of Wayne's VCE model case-erector systems, which assemble corrugated cartons at the rate of 80/min. Controlling motion in these systems with CD couplings is equally important as in Wayne's inserters. The VCE case erectors employ CD couplings mounted to gearbox shafts. Two are standard-model 6F45 couplings that transmit horizontal, rotary motion and provide zero backlash during operation and also when the system's clutch mechanism is actuated. This clutch mechanism is positioned on the vertical shaft of the gearbox and is composed of a torque-limiting clutch assembly and a special Zero-Max CD coupler. This device allows an operator to manually stop and restart the feeding mechanism as containers finish traveling through the system to complete a case-packer run.

"Overall, CD couplings give our systems excellent performance and service life since having replaced jaw and other type couplings a decade ago. The CD coupling was our first choice for the new SF-400, and it is very functional," Bachman says.