Lugs, usually triangular in cross-section, are common in mechanically timed carton packaging equipment. Engineers mount them at specific intervals on conveyor belts or flight chains to synchronize and maintain product position. Transferring products that are randomly spaced on a standard conveyor to a lugged machine, however, requires an automatic indexing system to place products precisely between each lug.
Additional hardware required to perform the indexing includes systems such as automatic loaders, timing screws, and smart belts. Smart belts, for example, typically use sensor input on five or six servo driven belts that take back-to-back or random products and space them out at consistent intervals. Such loading systems add significant cost, size, and complexity to the line.
A new wrap-around sleever, called the CS-80 from Adco Manufacturing Inc., self-indexes products from a lugless random infeed section using photoelectric-sensor input to servo-driven feeder and transfer sections. "The lugless design reduces machine size by two to three times and cuts costs from approximately $130,000 to about $70,000 or $80,000," according to Engineering Manager Colin Warnes. "This machine is much more compact, which frees up space in the plant for a more efficient layout. End users will also see a cost savings from not having extra parts, handling, or indexing equipment."
The CS-80 machine is designed to wrap paperboard sleeves around rectangular, oval, and round plastic trays or tubs of instant food products, ready-made chilled meals and processed meats. In a typical installation, products transfer from a standard conveyor to the infeed section of the sleever, which features variable speed belts to accelerate and space out any back-to-back items. A carton hopper above the infeed section stores a 24-inch long stack of flat sleeves.
Bosch Rexroth (Hoffman Estates, IL) supplies the PC-based electronic servo controls, brushless dc servomotors, and drives, responsible for tightly synchronizing the carton feeder mechanism and lugged chains in the transfer section.
Servos key to going lugless: This wrap-around sleever self-indexes product from a lugless random infeed section using photoelectric-sensor input to servo-driven feeder and transfer sections.
"Servos are the key to going lugless," explains Warnes. "The only reason we can do this is because both the feeder and transfer chains are fired on demand, based on sensor signals from in-bound product."
The feeder consists of a reciprocating arm with vacuum pick-up cups. A vacuum generator from PIAB North America (Hingham, MA) supplies the suction force. During operation, the carton feeder picks up a sleeve, moves it down over the incoming product, and waits for a trigger signal based on velocity data from the infeed belts, and position data from photoelectric sensors from ifm efector Inc. (Exton, PA). When triggered, it releases the sleeve right on top of the entering product, returns to pick another sleeve, and the cycle repeats. Once the sensor detects the presence of the sleeve on the product, it triggers the servo controller to actuate three lugged chain mechanisms. These are the only lugs on the machine, Warnes notes. The lugged chains transfer the container and flat sleeve together into the overhead conveyor section, which is powered by two ac gearmotors from Panasonic Industrial Co. (Milpitas, CA). Because these gearmotors achieve tight speed control, Adco Manufacturing engineers were able to come up with a split overhead conveyor design that lifts away for easier clearing of jams.
In previous applications it was difficult to remove products from under the conveyor, notes Warnes. The CS-80 solves that problem with a cantilevered pivot assembly that allows the two halves of the overhead conveyor to pivot upwards. "Because the gearmotors hold speed to within 2% speed variation, we can run the two halves of the overhead conveyor completely independent of each other, and use the split design," says Warnes. Panasonic also supplies smaller gearmotors for the infeed, squaring, and discharge sections on the machine.
Flexible grippers on the overhead conveyor apply pressure and compensate for overfilled or bulging products. As it moves through a series of folding plows and deadplates, the sleeve gets wrapped around the product. A pressurized gluing unit from Nordson Corp. (Duluth, GA) applies a bead of glue before the final flap is secured around the product. The finished product exits the machine on a set of discharge rollers.
The machine handles both full and partial length sleeves on single-count products, and runs at speeds up to 80 sleeves/minute. Wrap around sleeves have been used in packaging for 30 or 40 years. Because two sides of the carton are open, it saves money by conserving paperboard. It also allows the consumer to see the product on the shelf, as it's not completely hidden inside a box. Warnes says, "Essentially, the CS-80 brings wrap-around sleever technology down to a more affordable level with a more compact, yet more advanced design."
|Contact Colin Warnes, Adco Manufacturing, 2170 Academy Ave., Sanger, CA 93657; Tel: (559) 875-5563; Fax: (559) 875-7665; E-mail: firstname.lastname@example.org; or Enter 501.