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Overhead Conveyor Enclosed Track

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The overhead conveyor industry has come a long way since a young engineer by the name of Jervis B. Webb teamed up with a 20th century manufacturing revolutionary named Henry T. Ford. Images of the Charlie Chaplin movie short on the assembly line come to mind, which was avante garde at the time. Industrial engineering profoundly changed during this period of time. The I-beam overhead conveyor was conceived and developed to set up an assembly line into a synchronous single line layout of progressive tasks.

These overhead conveyors have the following advantages over the traditional belt and roller type floor conveyors:

  • product was non-conveyable on other conveyor designs
  • maximize plant layout by utilizing unused overhead space (cubic utilization)
  • free up valuable floor space for manufacturing equipment and operating personnel
  • smaller radii for the vertical and horizontal bends can be achieved

The continuous chain conveyor path:

  • saves in drives.
  • reduces costly controls when making a transfer or change in direction.
  • by not transferring between-conveyors the product damage is minimized.
  • inventory can be easily controlled via FIFO.

The bottom line in today’s manufacturing environment is to maximize the efficiency of the capitalized equipment in harmony with the manpower. Work in process is costly both in inventory and storage space. Work that is in the queue or ready maximizes the process uptime. These are fertile conditions for the power and free non-synchronous conveyors. Power and free not only incorporates the above listed overhead solutions but further enhances the following situations or applications:

The conveyor can be divided into separate distinct zones:

  • delivery
  • buffer or storage
  • sortation (varied product mix into various spurs)
  • process
  • loading and unloading

The product can be spaced or changed in speed by merging onto a separate chain.

The product can be closely packed via bias banking.

The part clearances can be regulated by the release from air operated stops, which is important for:

  • loading and unloading
  • queuing infront of process equipment or assembly areas
  • reducing oven space

Bypass spurs and re-circulation loops can efficiently control the product process sequencing.

Lift sections can aid in dipping operations or when tight elevation changes are required.

Each individual carrier can be held in an air operated stop which will achieve:

  • higher quality in the process
  • locational accuracy when interfacing with robots
  • each zone can work independent for the balance of the system

The 21st century has seen a movement from the traditional structural I-beam type overhead conveyors to the enclosed track design. In the late 1960’s the enclosed track conveyor systems emerged. By the mid 1970’s the power and free version of enclosed track conveyors was in its infancy.

The advantages of the enclosed track when compared to the I-beam overhead conveyors are:

  • lower cross section height
  • finger pinch points are reduced with internally running conveyor chain
  • prevents contamination of the conveyor chain and the product below
  • smaller radii on horizontal and vertical bends
  • some designs allow an inverted “slot up” position with minimal or no modifications

The bolted assembly is more suited to the enclosed track, than the I-beam, because the chain and trolleys run inside the track section. Ford Motor Company’s, Body & Assembly engineering developed the bolted construction modular build specifications almost 15 years ago, which incorporate the following advantages:

  • The assembly is considerably easier then onsite welding.
  • Onsite installation time is greatly reduced which reduces downtime and allows more of a window of opportunity for the commissioning phase.
  • Shop test set-ups can be broken down and reassembled easier.
  • The air piping and shop pre-wire can be easily incorporated into a bolt together module.
  • The ‘mechano set’ design transcends into the engineering and the entire system can be prefabricated with a match marked layout drawing
  • More adaptable to layout changes and retrofits.

The material handling challenges of the future include shorter leadtimes, space restrictions, cost effectiveness and flexibility to layout retrofits are met head-on with the bolted and enclosed track solution. The ingenuity and foresight of Misters Webb and Ford have withstood the test of time with these minor improvements. The mechanical equipment designs are basically intact with the major changes in the electrical controls portion of the system.


Published in Metal Finishing, February 2003


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