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Space-Saving Diverter
Rodless cylinder provides compact, integrated solution for conveyor systems
Al Presher, Contributing Editor -- Design News, April 1, 2009
Manufacturing and packaging facilities move and sort tons of bulk on conveyors, but the sorters, diverters and pull-offs that route products must be as trim as possible to make the most of valuable floor space. Engineers at Hytrol Conveyor Co. needed a more effective, space-saving solution when designing a diverter for an overhead pull-off system that would divert 150-lb boxes to a different conveyor line.
"Our conveyors are used to move products down the line, divert them to the next station in the manufacturing process or, if a product is defective, divert them to a reject line," says Jackie Smith, an application engineer at Hytrol. "When we needed to design a diverter that was more compact and could be simply integrated into our systems, we decided to employ a different type of actuator."
The traditional actuator used to operate diverters on a conveyor system is a pneumatic rod cylinder. Normally, a rod cylinder with up to a 48-inch stroke would be mounted off to the side, perpendicular to the conveyor, and operate a paddle that pushed a product off the conveyor or diverted it to a different line. However, these rod-style diverters consumed a lot of space because the cylinder extended about 48 inches beyond the width of the conveyor.
When floor space is at a premium, Hytrol now offers a framed overhead diverter design that uses a Tolomatic BC2 rodless pneumatic actuator. The BC2 actuator's length is the same as the conveyor's width, and the carriage moves entirely within the length of the actuator.
Tolomatic
"The BC2 actuator is a space saver," says Guy Holloway, president of Fraleigh Co., the local distributor that helped design the application. "The length of the rodless actuator is the same as the width of Hytrol's conveyor, making it much simpler to work it into new or retrofitted diverter stations. It can be mounted over or under the conveyor."
A rodless band cylinder actuator contains its stroke within the length of the cylinder itself. For example, a 2-inch bore rodless band cylinder, with a 48-inch stroke, can provide 43 percent space savings compared to an equivalently sized rod cylinder. A rodless actuator also guides and supports the load throughout the entire stroke length, so there is minimal bearing wear and load deflection compared to rod-style cylinders. As a result, bending moments are better controlled, resulting in longer wear without seal or bearing stress.
Hytrol initially looked at other types of actuators, but liked the size and performance of the rodless actuator and found it easy to mount within its pull-off design. Rodless cylinders offer equal piston areas in both directions, eliminating load variations. Plus, the load and piston have a floating connection, resulting in less friction and longer seal life.
"In Hytrol's overhead diverter design, the actuator has to move a large triangular paddle that pushes boxes weighing up to 150 pounds," says Holloway. "This can create very high bending moments on the actuator's carriage and guide bearings. The BC2's carriage has a very robust bearing system with higher side-load capacity. When designing for very high bending moments, sometimes we specify dual carriages on the actuators to distribute the forces."
Tolomatic's BC2 rodless pneumatic actuator: http://designnews.hotims.com/23101-598
For more fluid power/power transmission news, visit http://designnews.hotims.com/23101-599.
