A servomotor powers pick-and-place motion in an innovative packing machine by means of a backlash-free coupling. The coupling damps out shock and vibration from the packing head's reciprocating and intermittent motion.
The packing machine, developed by Schneider Packaging Equipment Co. Inc. of Brew-erton, N.Y., contains three heads, each holding 16 vacuum cups. Each cup grips the top of a single 4-oz juice container. Each head positions and stacks 16 juice containers simultaneously. Once three tiers of 16 cups are in place, the machine folds and seals case flaps to produce a container ready for shipping.
A 2-hp servomotor working through a speed reducer moves the head clusters back and forth horizontally along a track to produce pick-and-place action. Horizontal movement must synchronize closely with the vertical action of the vacuum heads (produced with air cylinders). The combination of intermittent and reciprocating motions, especially at high speeds, puts a significant load on the drivetrain components.
"We needed to position a coupling between the case packer servomotor and the speed reducer/timing belt," explains Schneider design engineer Joseph Morak. "The coupling compensates for backlash and provides accurate pick-and-place motion."
The need for torsional rigidity (to avoid the possibility of backlash) eliminated bellows-type couplings from consideration. Tests revealed that a CD Coupling from Zero-Max Inc., Plymouth, Minn., would work well within equipment operating parameters. These include 4,000-rpm maximum motor speed, 31-lb-in. maximum torque, and linear speeds as high as 4 ft/sec.
The 6P26C coupling specified for the machine is a Double Flex model that incorporates a durable composite disc material in a special open-arm design. It transmits torque between shaft-coupling hubs while damping shock and vibration, promoting long life and smooth operation.
The CD coupling incorporates machined hubs with keyway bores, or keyless clamp-type mounting hubs for easy installation. The low inertia of its patented design helps avoid system resonance. The coupling also has enough flexibility to handle higher angular and axial misalignments.
Schneider built the automatic case packer for Jersey Juice Inc. of Ewing, N.J. The system operates at 700 cups/min. Large quantities of the ready-to-drink nonrefrigerated juice products it handles go to national markets.