'Rotary-shuttle' blow molder combines best of two worlds.

A new four-station continuous-extrusion blow molder employs a novel "rotary-shuttle" concept that's said to combine the advantages of both wheel and shuttle machines - namely, high throughput rates and finishing the container neck in the mold. Designed to accommodate multiple parisons, multilayer coextrusion, and in-mold labeling of containers from 12 oz to 2.5 gal, the new machine offers an optimum ratio of productivity to capital cost, according to James Sheely, sales manager of the Plastics Div. of R&B Machine Tool Co., Saline, Mich.

Although not widely known in the plastics machinery business, R&B Machine Tool first introduced a line of shuttle blow molding machines in 1978 and indexing-wheel rotary machines with six and eight stations in 1986. In addition, R&B has built several proprietary continuous-wheel, captive-parison machines for a large international blow molder since 1982.

The new four-station indexing wheel includes refinements such as an extra-wide platen that reportedly provide higher productivity and flexibility.

MORE BANG FOR THE BUCK

In Sheely's view, the new Rotary IV offers more capacity for less cost than required with shuttle machines. He says the four-parison Rotary IV offers double the output of a double-shuttle machine at only 20-25% higher cost.

The Rotary IV has an 18 x 20 in. platen that accommodates a wide range of existing shuttle blow molds with the addition of a new backing plate. The large platen can handle up to four free-hanging parisons on 5-in. centers. The four-parison configuration can handle up to 16 cavities with rates of up to 4800 bottles/hr.

All machine movements are driven by a 7.5-hp motor and are mechanically timed for accuracy. Indexing is accomplished with cam boxes, so there is no starting and stopping of the motor. The cam station is rated at 40 indexes/min.

At the first index position, the blow pin is inserted in the mold, which remains closed for 75% of the wheel's rotation. Blowing time ranges from 65% to 68% of the time the mold is closed, depending on the number of parisons.

ACCURATE SETUP

A separate adjustable blow-pin assembly is mounted on each mold station to aid alignment. The machine also has a separate parison programming cylinder for each parison, allowing heads to be balanced more easily and making it possible to compensate for tooling variations or slight temperature variations, Sheely says. "It gives you a better running window and more flexibility in running the machine," he adds. The extruders operate on a pivoting lift system, which keeps the heads as close to the tops of the mold as possible.

Bottles are provided with a calibrated finish when the blowpin comes in contact with a cutting device at the top of the mold. In-mold container finishing allows the machines to be used for personal-care bottles as well as larger containers.

POSITIVE BOTTLE HANDING

All bottles exit the machine at the same location. Moils are stripped as the blow pin is pulled from the bottle. Takeout pins are inserted into the neck of the bottle prior to mold opening. When the mold opens, the container is indexed into the tail-removing device and then transferred to the trimming operation, if required, or directly to a case-packing system.

Another advantage of the rotary machines is that in-mold labeling can be accomplished without cycle interruption, Sheely points out. The IML unit is a modular system in which one unit can be set up to handle one to four parisons. Labeling takes place at the last index position. The labeling mechanism takes approximately 3 sec to pick up the label, transfer it to the mold, and retract out of the way. The system can handle plastic or paper labels and can label either the front or back or both at once.

Price for a monolayer four-station machine is a little over $1 million, not including molds or options such as IML, automatic screen changer, or trimmers. R&B holds three patents on its Rotary Line, and three more are pending on the Rotary IV, says Sheely.